Tighten up the tC's steering? Steering rack bushings?
10-03-2005, 04:43 PM
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Tighten up the tC's steering? Steering rack bushings?
OK, I went from an AWD car to a FWD car so maybe I still need to get used to bump steer and such...
I think the tC's steering could be tightened up a bit...it sometimes feels a bit sloppy...
On the WRX, lots of guys use stiffer steering rack bushings...anyone know of any available for the tC? Any other ideas?
As you can see, I have a good amount of suspension upgrades... although I feel really flat in the corners now and there's very little body roll, I would still like to do domething about the steering feel...
Thanks!
I think the tC's steering could be tightened up a bit...it sometimes feels a bit sloppy...
On the WRX, lots of guys use stiffer steering rack bushings...anyone know of any available for the tC? Any other ideas?
As you can see, I have a good amount of suspension upgrades... although I feel really flat in the corners now and there's very little body roll, I would still like to do domething about the steering feel...
Thanks!
10-03-2005, 06:05 PM
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The bump steer is caused by the severe lowering the car which results in changing the arc of the tie rod versus the lower control arm. This results in a severe lowering of the roll center which required extra stiff sway bars and fairly stiff springs to help alleviate the problem of the roll center but does nothing for bump steer and can cause a lack of grip as the two outside tires are forced to carry most of the cornering load no matter how flat you keep the car from springs and sways.
This is compounded by the tremedous leverage the 62 lb glass roof has over the roll center due to the center of gravity being so far above the roll center.
One fix we are doing is installing a 15 lb CF/Kevlar roof, amost done with it now
We are also installing a CF hood a bit later, want to do a hatch but not legal in our SCCA class, and our seats are far lighter as well as seat belts, etc, anything we can move the weight down with or remove it completely and still have a satisfactory daily driver capable car we are doing.
Lo Bux and I are both working on ideas for solutions to these problems. One is more a band aid approach, fitting in drop mounted control rod ends to lower the angle of the A arm back to an acceptable degree. That alone can cure the very low roll center issue which would help maintain proper weighting of the tires during cornering. Lo is looking into going a bit further with this, I am waiting to see what he comes up with.
Another idea is to raise the inner control arms with ecentric bushings but not are available, yet, I am temped to cut and reweld the inner pic up points but again, I have rules to abide by in my class;)
For those that do not take this as seriously or have the time, or place to do such things or even the desire, I advise that you do not drop the car more than an inch or so, run stiffer springs but not horribly stiff, a fairly stiff rear sway, milder or even stock front one and no not install anything very high up in your car, anywhere;) Then get the widest wheels with the best offset you can, 8.5 with a 42 (could be 48, ask Lance) is the very best because of the load on the bearings and the suspension will work better. I had to go with 17x8 +35mm which offsets the center of the wheels outward by 1/2", not quite as good but tolerable.
The outer mount drop may fix or take care of the bump steering issues, we will find out in time. (I personally do not have much of a problem with it for some reason, it seems it should be worse. )
Rick
This is compounded by the tremedous leverage the 62 lb glass roof has over the roll center due to the center of gravity being so far above the roll center.
One fix we are doing is installing a 15 lb CF/Kevlar roof, amost done with it now
We are also installing a CF hood a bit later, want to do a hatch but not legal in our SCCA class, and our seats are far lighter as well as seat belts, etc, anything we can move the weight down with or remove it completely and still have a satisfactory daily driver capable car we are doing. Lo Bux and I are both working on ideas for solutions to these problems. One is more a band aid approach, fitting in drop mounted control rod ends to lower the angle of the A arm back to an acceptable degree. That alone can cure the very low roll center issue which would help maintain proper weighting of the tires during cornering. Lo is looking into going a bit further with this, I am waiting to see what he comes up with.
Another idea is to raise the inner control arms with ecentric bushings but not are available, yet, I am temped to cut and reweld the inner pic up points but again, I have rules to abide by in my class;)
For those that do not take this as seriously or have the time, or place to do such things or even the desire, I advise that you do not drop the car more than an inch or so, run stiffer springs but not horribly stiff, a fairly stiff rear sway, milder or even stock front one and no not install anything very high up in your car, anywhere;) Then get the widest wheels with the best offset you can, 8.5 with a 42 (could be 48, ask Lance) is the very best because of the load on the bearings and the suspension will work better. I had to go with 17x8 +35mm which offsets the center of the wheels outward by 1/2", not quite as good but tolerable.
The outer mount drop may fix or take care of the bump steering issues, we will find out in time. (I personally do not have much of a problem with it for some reason, it seems it should be worse. )
Rick
10-03-2005, 06:10 PM
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Now to the steering rack bushings
Any stiffening you do will cause a bit more noise transfer into the cabin of the car, just need to be aware of that.
I will see about repouring mine in eurathane when I drop the whole subframe soon.
What I really want is faster steering so bought a really sweet little billet and of course steel internals, 1.5 lbs total, and 1.5:1 steering quickener which may be a bit too quick at 11.7:1 or so when installed and it will require alot of fabrication to get it to work, fairly unreversable as well once done so holding off until we get the car faster to see if I can keep up autocrossing in the really twisty sections. Our last car was fast enough I ended up flailing at the wheel trying to turn it fast enough instead of actually steering properly through those turns.
Rick
Any stiffening you do will cause a bit more noise transfer into the cabin of the car, just need to be aware of that.
I will see about repouring mine in eurathane when I drop the whole subframe soon.
What I really want is faster steering so bought a really sweet little billet and of course steel internals, 1.5 lbs total, and 1.5:1 steering quickener which may be a bit too quick at 11.7:1 or so when installed and it will require alot of fabrication to get it to work, fairly unreversable as well once done so holding off until we get the car faster to see if I can keep up autocrossing in the really twisty sections. Our last car was fast enough I ended up flailing at the wheel trying to turn it fast enough instead of actually steering properly through those turns.
Rick
10-03-2005, 06:32 PM
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Hmmm...thanks for all the info!
A little technical for me to be honest... I certainly won't be modifying my car anywhere near what yours will be!
As you can see, I have the TRD stut/spring combo. I like it alot and really enjoy the improved handling and the lessening of the body roll.
If the tC's steering ratio or overall feel could be improved fairly easily, I think it could be a highly desirable mod that many would take advantge of.
The bump steer that I mentioned was there even when the car was stock...it's really not bad...only when I'm driving at slow speeds or slowing down at a red light do I notice that bumps and what not slightly pull the wheel this way and that...
A little technical for me to be honest... I certainly won't be modifying my car anywhere near what yours will be!
As you can see, I have the TRD stut/spring combo. I like it alot and really enjoy the improved handling and the lessening of the body roll.
If the tC's steering ratio or overall feel could be improved fairly easily, I think it could be a highly desirable mod that many would take advantge of.
The bump steer that I mentioned was there even when the car was stock...it's really not bad...only when I'm driving at slow speeds or slowing down at a red light do I notice that bumps and what not slightly pull the wheel this way and that...
10-03-2005, 07:15 PM
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Most welcome, just hoping a few others can see the effects of lowering a car to much
I would advise getting the rear sway bar as well then;)
Steering ratio, no, not easy or low cost to change.
Try a bit more air in your tires, feel will improve a bit but do not go to far, will lose traction in the rain, ride to stiff, wear in the middle, etc.
You may be suffering more from improper toe alignment, should be zero out back and up front about 1/16th" toed in. If toed out or even zero it can wonder like that as well as from bump steer.
It can also be partly from the tread design of the tires, big center grooves can lead to that issue.
Or loose tie rod ends but they normally make easily heard noises if loose.
Rick
I would advise getting the rear sway bar as well then;)
Steering ratio, no, not easy or low cost to change.
Try a bit more air in your tires, feel will improve a bit but do not go to far, will lose traction in the rain, ride to stiff, wear in the middle, etc.
You may be suffering more from improper toe alignment, should be zero out back and up front about 1/16th" toed in. If toed out or even zero it can wonder like that as well as from bump steer.
It can also be partly from the tread design of the tires, big center grooves can lead to that issue.
Or loose tie rod ends but they normally make easily heard noises if loose.
Rick
10-03-2005, 08:25 PM
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I didn't see better tires in the list of mods for suby2scion. I'd get rid of the RE52 Potenzas first.
Rick's description of bump steer is good, but in layman's terms it means the angle of the wheel changes as the suspension moves up and down. Ideally, it should not. It is nearly impossible to get perfect because your control arm and your tie rod end would have to describe the exact same arc. If you understand steering geometry, it's just not possible. There is always some, and regardless of how you raise or lower the car, it's fundamental to the design and can't be changed without doing something fairly radical like changing the length of the steering rack, or as Rick alluded, changing the location of the pick up point for the tie rod end.
None of this is simple or easy to do.
That all said, I suspect what you are experiencing is not true bump steer at all. It's more likely a combination of crappy stock tires and low air pressure. I'd bump the fronts up to 34 psi, and the rears to 32. See if it feels better. It probably will, and it will be a lot simpler and cheaper than what Rick and I are doing.
Rick's description of bump steer is good, but in layman's terms it means the angle of the wheel changes as the suspension moves up and down. Ideally, it should not. It is nearly impossible to get perfect because your control arm and your tie rod end would have to describe the exact same arc. If you understand steering geometry, it's just not possible. There is always some, and regardless of how you raise or lower the car, it's fundamental to the design and can't be changed without doing something fairly radical like changing the length of the steering rack, or as Rick alluded, changing the location of the pick up point for the tie rod end.
None of this is simple or easy to do.
That all said, I suspect what you are experiencing is not true bump steer at all. It's more likely a combination of crappy stock tires and low air pressure. I'd bump the fronts up to 34 psi, and the rears to 32. See if it feels better. It probably will, and it will be a lot simpler and cheaper than what Rick and I are doing.
10-03-2005, 09:08 PM
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Thanks for the info guys!
I do have the TRD rear sway, just for the record...
And yes I'm still on the crappy Potenzas though better tires are coming soon. I'm concerened that sticker tires may increase this sensation as they would be more likely to follow the groves in the road?
And off of bump steer and back to steering feel...no one knows of any replacement steering rack bushings as of yet?
Thanks!
I do have the TRD rear sway, just for the record...
And yes I'm still on the crappy Potenzas though better tires are coming soon. I'm concerened that sticker tires may increase this sensation as they would be more likely to follow the groves in the road?
And off of bump steer and back to steering feel...no one knows of any replacement steering rack bushings as of yet?
Thanks!
10-03-2005, 09:21 PM
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No, no steering rack bushings. There are four mount bolts with rubber bushings. It is mounted to the top of the subframe, so you'd need to (at the very least) lower the subframe just to get to the bushings. It would be a real PITA job just for some bushings. Page 51-20 in the FSM shows you what they look like in the steering rack. Chapter 51 also covers everything you need to know about getting the rack out and in again. It won't be easy for the average home mechanic.
10-03-2005, 09:25 PM
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i know you guys say rear sway bar, i know this really reduces the body roll but does it really give you that much more grip around corners?? like a rear progress bar is it really that neccessary?
10-03-2005, 09:50 PM
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1. Tires - no other change will affect the car's handling more.
2. Springs & shocks/coilovers - once you have grip, now you need control of the wheels.
3. Swaybars - now that the car is lowered and cornering faster, roll control is the order of the day.
4. Alignment to more aggressive specs - more camber, correct toe = improved cornering speeds.
5. Strut tower bar - now you need to maintain the negative camber you've got by changing everything else.
6. No more bolt-ons worth a lot. At this point, you'll need to make hard decisions about the car's intended purpose. Replace all rubber bushings with solid ball mount devices throughout the entire suspension. You need to seriously consider a major diet to get weight off the roof and lower the center of gravity. You need to re-engineer the suspension to get the roll center back up where it belongs, and set the roll axis to balance the car properly. Serious chassis stiffening through either expandable foam in the open chassis sections or a complete roll cage to dramatically improve chassis stiffness are next. More cubic dollars on weight reduction with exotic materials replacing heavier steel and aluminum in key places on the car is next.
Since we've already spent about 10 x the value of the tC, there could only be one reason for doing this: someone else is footing the bill. And, it isn't very streetable at step 6 anymore either (but Rick will tell me it's not so bad I'm sure).
2. Springs & shocks/coilovers - once you have grip, now you need control of the wheels.
3. Swaybars - now that the car is lowered and cornering faster, roll control is the order of the day.
4. Alignment to more aggressive specs - more camber, correct toe = improved cornering speeds.
5. Strut tower bar - now you need to maintain the negative camber you've got by changing everything else.
6. No more bolt-ons worth a lot. At this point, you'll need to make hard decisions about the car's intended purpose. Replace all rubber bushings with solid ball mount devices throughout the entire suspension. You need to seriously consider a major diet to get weight off the roof and lower the center of gravity. You need to re-engineer the suspension to get the roll center back up where it belongs, and set the roll axis to balance the car properly. Serious chassis stiffening through either expandable foam in the open chassis sections or a complete roll cage to dramatically improve chassis stiffness are next. More cubic dollars on weight reduction with exotic materials replacing heavier steel and aluminum in key places on the car is next.
Since we've already spent about 10 x the value of the tC, there could only be one reason for doing this: someone else is footing the bill. And, it isn't very streetable at step 6 anymore either (but Rick will tell me it's not so bad I'm sure).
10-03-2005, 10:23 PM
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As allways, Lance is right on the money, we are not even done and it is getting to be not fun on the street but sure is in all the super twisty mountain roads around here but is a bit stiff for some of them, spring rate that is, need softer springs generally on bumpier roads to maintain tire contact.
I have thought about all solid ball mounts, dang would make a big difference but sure would be noisy and hard on things. Just having them on the top of the struts is rather noisy and a bit harsh at times, sure makes it handle better though.
Rick
I have thought about all solid ball mounts, dang would make a big difference but sure would be noisy and hard on things. Just having them on the top of the struts is rather noisy and a bit harsh at times, sure makes it handle better though.
Rick
10-07-2005, 01:34 PM
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Rick,
Are you planning on marketing the CF/Kevlar roof? If not, do you have pictures? I think it is a great idea, I could care less about the glass sunroof I'm all about the autocross/track days.
Oh, you all may know this by now but there is a very good chance that a "tuner edition" tC will be coming next year that will cost a little less but more importantly weigh a little less. Will come with fixed glass roof (won't open), steel wheels and a little less content than the regular model. Next best thing to a "club" or "spec" model tC.
Are you planning on marketing the CF/Kevlar roof? If not, do you have pictures? I think it is a great idea, I could care less about the glass sunroof I'm all about the autocross/track days.
Oh, you all may know this by now but there is a very good chance that a "tuner edition" tC will be coming next year that will cost a little less but more importantly weigh a little less. Will come with fixed glass roof (won't open), steel wheels and a little less content than the regular model. Next best thing to a "club" or "spec" model tC.
10-07-2005, 04:16 PM
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South,
Sounds like the perfect car except it should have a CF or aluminum or at least steel roof
I did not make the roof myself but was prepared to do so if I had to, huge undertaking that would of been.
The one I have was designed to be installed over the steel frame that supports all the hardware for the glass roof. You would have to bust out the rear glass as glue on and no room to get to it to cut it out(took it to a pro after I gave up) I was going to bust it out but made a call and found out it is a $950 piece so it is going on Ebay along with the rest of the parts.
So, we had to figure out a new way to attach the roof, got it ready to install today finally. There was alot of fitment issues that would of been just the same with, probably worse really, if we had kept the steel mounting hardware inplace. The roof we have is not not something very marketable just yet, if it even does come out, they are not sure will sell it yet. We had in on and off the car at least 10 times trimming this and that to get it right. Then had to figure out new gaskets, mounts, etc.
The cool thing is, stock roof is 62 lbs, this one is 15 lbs, the original design for mounting would of added another 7-8 lbs, our method will add barely over a lb
And, we have room to cross brace the roof area, great chassis stiffening project about to commence
We are really taking our time on this to get it right, perfectly aligned and fitted, very well mounted and supported. It will be thermally and accoustically treated with super low weight but very effective materials as well, maybe a pound total.
Combined with out super stiff structural foam filled chassis, crossbraced roof, dropping approx 45 lbs off the top of the car, we expect alot of gain in the handling department
I will try to get the manf to build more of these, hopefully with some changes I will recommend for easier install.
Rick
Sounds like the perfect car except it should have a CF or aluminum or at least steel roof
I did not make the roof myself but was prepared to do so if I had to, huge undertaking that would of been.
The one I have was designed to be installed over the steel frame that supports all the hardware for the glass roof. You would have to bust out the rear glass as glue on and no room to get to it to cut it out(took it to a pro after I gave up) I was going to bust it out but made a call and found out it is a $950 piece so it is going on Ebay along with the rest of the parts.
So, we had to figure out a new way to attach the roof, got it ready to install today finally. There was alot of fitment issues that would of been just the same with, probably worse really, if we had kept the steel mounting hardware inplace. The roof we have is not not something very marketable just yet, if it even does come out, they are not sure will sell it yet. We had in on and off the car at least 10 times trimming this and that to get it right. Then had to figure out new gaskets, mounts, etc.
The cool thing is, stock roof is 62 lbs, this one is 15 lbs, the original design for mounting would of added another 7-8 lbs, our method will add barely over a lb
And, we have room to cross brace the roof area, great chassis stiffening project about to commence
We are really taking our time on this to get it right, perfectly aligned and fitted, very well mounted and supported. It will be thermally and accoustically treated with super low weight but very effective materials as well, maybe a pound total.
Combined with out super stiff structural foam filled chassis, crossbraced roof, dropping approx 45 lbs off the top of the car, we expect alot of gain in the handling department
I will try to get the manf to build more of these, hopefully with some changes I will recommend for easier install.
Rick
10-07-2005, 07:32 PM
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Rick,
Sounds a little more involved that I thought it would be. I don't know that I was going to take it to the extreme that you are. I figured I would find a way to replace the glass with CF/Kevlar in case I ever wanted to convert it back to glass. Do you think it would be difficult to replace the three glass panels with three CF/Kevlar assuming the panels attached like the glass? I realize this way wouldn't save as much weight but I'm not as hardcore as you are.
Well thanks for being the guinea pig. It's great to have you out there pushing the boundries.
Sounds a little more involved that I thought it would be. I don't know that I was going to take it to the extreme that you are. I figured I would find a way to replace the glass with CF/Kevlar in case I ever wanted to convert it back to glass. Do you think it would be difficult to replace the three glass panels with three CF/Kevlar assuming the panels attached like the glass? I realize this way wouldn't save as much weight but I'm not as hardcore as you are.
Well thanks for being the guinea pig.
It's great to have you out there pushing the boundries.
10-07-2005, 07:53 PM
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Most welcome
Problem is, the front two pieces are bolt in, not a problem, the rear is glued in and has to be broken out to remove it. It is sold as part of the surrounding metal structure and lists for $950!!!!!
So, you end up only saving maybe 10 lbs at the very most, maybe not even that much, the panels would cost quite a bit as well.
You could save more by stripping everything out but then would have nothing to mount the two pieces on, have to build mounts, etc, etc......
We took the time to look at all the ideas we could come up with.
Rick
Problem is, the front two pieces are bolt in, not a problem, the rear is glued in and has to be broken out to remove it. It is sold as part of the surrounding metal structure and lists for $950!!!!!
So, you end up only saving maybe 10 lbs at the very most, maybe not even that much, the panels would cost quite a bit as well.
You could save more by stripping everything out but then would have nothing to mount the two pieces on, have to build mounts, etc, etc......
We took the time to look at all the ideas we could come up with.
Rick
07-09-2006, 02:41 PM
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OK Need Help Please
I'm not a tuner really. Although I wish i knew a bit more about some things. I dont where you guys learned all this stuff.
I have a scion TC and I love it the way it is.. if only for the severe bumpy ride. I think it turns a little sloppily as well. I swear I can feel it hop sometimes especially when I make right turns.
I want a tight turning machine...with no sway.... but I hate feeling every little pebble in the road. Is there a solution? I know that there is a little compromise if i want a smoother ride. What is the different between the front sway and the rear sway bars that everyone puts in their cars? Do I need both? And why didnt Toyota just put them in the car to begin with?
I dont care about lowering my car at all. Not my style. I think my car looks good the way it is.
Oh and one more thing...... can anyone recommend replacement bulbs for the car that work well with the TC? The stock ones seem so dim..
I read a lot on the forums.. but it just isnt sinking in.. its hard to understand when you guys get so technical. I have a hard time understanding difference between coilovers, struts, springs, etc. When people mention suspension do they mean all three of those things?
Sorry if these seem like stupid questions to you.
I have a scion TC and I love it the way it is.. if only for the severe bumpy ride. I think it turns a little sloppily as well. I swear I can feel it hop sometimes especially when I make right turns.
I want a tight turning machine...with no sway.... but I hate feeling every little pebble in the road. Is there a solution? I know that there is a little compromise if i want a smoother ride. What is the different between the front sway and the rear sway bars that everyone puts in their cars? Do I need both? And why didnt Toyota just put them in the car to begin with?
I dont care about lowering my car at all. Not my style. I think my car looks good the way it is.
Oh and one more thing...... can anyone recommend replacement bulbs for the car that work well with the TC? The stock ones seem so dim..
I read a lot on the forums.. but it just isnt sinking in.. its hard to understand when you guys get so technical. I have a hard time understanding difference between coilovers, struts, springs, etc. When people mention suspension do they mean all three of those things?
Sorry if these seem like stupid questions to you.
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