Str8 Six bump steer modification
Discussion
Session said:
Tyres were fine when kit was fitted. I had the kit fitted by local TVR specialist and I'm sure he'd have mentioned something if they weren't. Been running the tyres the same since I got the car back in August last year and not had any issues.
All I can think is it needed more adjustment than initially thought.
All I can think is it needed more adjustment than initially thought.
Sorry to hear of your prob. I think you'll find that the only cause of that can be MASSIVE toe-out from poor geo setting after installation, which lines up with your initial impression of heavy steering. I drove another car with an 'accidental' 5mm of toe-out last year for 70 miles, which felt pretty heavy and would have destroyed the tyres.
If it was me I'm afraid I'd be claiming for a set of tyres! I've had the lower steering arms on mine for 400m, no bump steer and no tyre wear.
I'm not bothered about claiming for tyres, they were only about 1mm off needing to be replaced anyway so it's just brought forward the need by a month or two.
The car didn't feel that horrible at all weirdly otherwise I'd have got it looked at sharpish. It was a little heavier dead central as though it was a bit more tramliney. The car is going in for a service in a week or two so the geo was gonna be fully re-set then and John at Sussex TVR did say it might be worth adjusting it a little more to help with the slightly heavier feeling in a straight line.
Having a new part fitted was going to change how it felt and the bump steer is loads loads better, in many ways I put faith i nthe guys who design the parts and teh setup done so taht gives me faith not to think tyres will be dying.
The car hasn't had any major knocks to put the geo out and both tyres have done exactly the same so it's not what a pothole woudl do.
The car didn't feel that horrible at all weirdly otherwise I'd have got it looked at sharpish. It was a little heavier dead central as though it was a bit more tramliney. The car is going in for a service in a week or two so the geo was gonna be fully re-set then and John at Sussex TVR did say it might be worth adjusting it a little more to help with the slightly heavier feeling in a straight line.
Having a new part fitted was going to change how it felt and the bump steer is loads loads better, in many ways I put faith i nthe guys who design the parts and teh setup done so taht gives me faith not to think tyres will be dying.
The car hasn't had any major knocks to put the geo out and both tyres have done exactly the same so it's not what a pothole woudl do.
after giving this a bit of thought, the mod raises the steering rack , so the suspension geo is not affected at all, however any alterations whatsover to the steering system will mean that the tracking will need to be completely reset.
I`d say that your chap in sussex who fitted this didn`t bother to re track the car afterwards, if he had, and done it properly your tyres would not be in the state they are now, as others have said, they have had this mod done and have had no problems at all, so the design of the mod is fine, but if its not fitted and set up properly then you will have problems.
I`d say that your chap in sussex who fitted this didn`t bother to re track the car afterwards, if he had, and done it properly your tyres would not be in the state they are now, as others have said, they have had this mod done and have had no problems at all, so the design of the mod is fine, but if its not fitted and set up properly then you will have problems.
Undoing bolts and replacing them can cause parts to go back in slightly different places, I believe the mod replaces the steering arms as well, old parts may have been bent slightly and steering will have been adjusted to correct this, with steering we are talking fractions of a degree and I'm quite shocked that any professional garage would replace steering parts without a geometry check afterwards.
Now I'm no expert on mechanicals (I learn as I go) I'm thinking that as the mounting hole goes higher to flatten the angle of the steering arm/rack then it pushes the wheel/hub assembly outwards and the adjustments made after were nowhere near enough as that woudl explain the wear and heavy feeling steering moving from dead centre..
I've ordered new tyres so will get the wheels on the car and straight to somewhere to get geo setup. Could do with the geo setup guidelines really to get it done local if John at Sussex TVR can't do it that soon.
I've ordered new tyres so will get the wheels on the car and straight to somewhere to get geo setup. Could do with the geo setup guidelines really to get it done local if John at Sussex TVR can't do it that soon.
the steering arm is bolted to the hub, the mounting hole is positioned higher as you say to give the steering rod a better alignment with the rack, yes you are right that the steering rod would be longer if you raise it up, but, you then shorten this by adjusting the track rod end on the end of the steering rod, this gives you the correct wheel alingment, ie toe in or toe out.
there should be no need to adjust the camber angle at all, the hub cannot be pushed in or out in its vertical plane as it is held by the balljoints at the top and bottom of the hub,so the wheel is where it should be before you started, but unless the tracking is adjusted the wheels will both be facing outwards, hence very excessive tyre wear.
assuming the t350 is the same as the sag, the settings from graham varleys manual are Toe in 1 to 2mm and camber .5 to .75 degrees negative.
there should be no need to adjust the camber angle at all, the hub cannot be pushed in or out in its vertical plane as it is held by the balljoints at the top and bottom of the hub,so the wheel is where it should be before you started, but unless the tracking is adjusted the wheels will both be facing outwards, hence very excessive tyre wear.
assuming the t350 is the same as the sag, the settings from graham varleys manual are Toe in 1 to 2mm and camber .5 to .75 degrees negative.
Session said:
It was toe in that was adjusted to Jason's recommendations when the mod was fitted. Will have to see what the outcome is.
IMHO they can't possibly have been set to Jason's recc setting, which is for toe-in exactly as the standard factory setting (regardless of the lowered steering arm) not toe-out. Working fine on mine, and bump-steer now eliminated. That pattern of rapid extreme wear can only be generated by very excessive toe-out.
So you'll be safe with the new front tyres, with wheels set for very slight toe-in, as per factory '5-to-6 minutes toe-in each side' for the T350 (which was confirmed to me by Neill Anderson the TVR suspension designer).
The 'minutes' measurement is 1/60th of a degree, and is what most geometry machines use, rather than the alternative measurement in mm at the wheel rim, as the rim is not entirely reliable due to tiny bumps and bends in it's surface.
Edited by tail slide on Monday 28th March 22:10
Firstlt I got some new tyres on her and as it was due a service anyway I got it straight in with John at Sussex TVR for a 12k service which would normally include a full geo setup etc anyway. The toe in was out as expected and John sorted me out nicely and it's now running great. The bump steer mod certainly makes a difference and my car is now runnign better than ever, very pleased.
Glad to hear all sorted Session. Dvs - IMHO it's a tweak for perfectionists, TVR steering has always had a little bump-steer compared to ultimate possible but most drivers aren't bothered by it. 2005 steering set-up for Sag (and presumably Tuscan2?) finally sorted it. This brings Tam/T350 to same level, and without needing steering rack raising.
tail slide said:
Basil Brush said:
I'm not sure I agree with this relating to earlier Tuscans. Mid corner compressions/bumps and firm braking on uneven roads could be pretty scary in mine before the mod.
OK, I was referring to Tam's/T350's Had my steering rack raised.
And swopped the (Eibach) springs front to rear (rear now 400, front 325).
And put on Toyo R1R's (R:255 and F:225).
Handling is really amazing, and it already was very good but in a different league now.
Can fully recommend this treament (spring setup for Tuscan only since it has such a big ass!).
And swopped the (Eibach) springs front to rear (rear now 400, front 325).
And put on Toyo R1R's (R:255 and F:225).
Handling is really amazing, and it already was very good but in a different league now.
Can fully recommend this treament (spring setup for Tuscan only since it has such a big ass!).
Surprising as it seems .......No!
400 Lbs on the rear and less on the front, in my case 375Lbs on the front is the way to go.
BUT>>>>>>> It does depend on how you are able to control the front rebound rate. The standard Gaz golds most likely need a re-valving. If you are using them, that will stop any "porpoising" on a series of high speed undulations from about 90 mph upwards. Also the harder rear springs really tame the Tuscans tendency to head for the Armco when shifting at full chat from 3rd to 4th, 7000Rpm at 130mph.The weight transference from the font to rear will require the stiffer springs at the rear. My car has a 49% rear and 51% front weight split and weighs in at 1158Kg now. A touch heavier now due to the heavier than standard 16" wheels/tyres, 18" wheels/tyres and the Sagaris disc brakes.
I run 255/35 x 18 R1R's front and rear. I have raised my steering rack by 15mm also. This transformed the cars handling for the better. As did cranking in over 5 degrees of catsor to the front wheels and some rear toe in. I am still playing with it but I really do feel as though I am at last close to getting the best out of my Tuscan.
This does all depend of course upon ones preferred style of driving.
Also I am about to fit the MK1 "S" splitter but I will give it a 20 degree angle of attack towards the road surface, unlike all the others that I have seen which seem to be almost parallel with the road surface.
I have also now built a new 383ci SBChevrolet for it. Hope to post the dyno results tomorrow on my link. I have changed the rpm at which the torque comes in and paid a lot of attention to matching it to the clutch, a McLeod twin plate, and the ultimate rev range of the motor. It is about 526Bhp now @ about 6300rpm with 446ftlbs of torque at about I think from memory 5500Rpm, but as I say, dyno sheet maybe tomorrow.
I have been rebuilding this 383ci motor with John Sleath Racing.
Don't forget I am building a GT..... not a racing car.
Regards.
Speed eight.
400 Lbs on the rear and less on the front, in my case 375Lbs on the front is the way to go.
BUT>>>>>>> It does depend on how you are able to control the front rebound rate. The standard Gaz golds most likely need a re-valving. If you are using them, that will stop any "porpoising" on a series of high speed undulations from about 90 mph upwards. Also the harder rear springs really tame the Tuscans tendency to head for the Armco when shifting at full chat from 3rd to 4th, 7000Rpm at 130mph.The weight transference from the font to rear will require the stiffer springs at the rear. My car has a 49% rear and 51% front weight split and weighs in at 1158Kg now. A touch heavier now due to the heavier than standard 16" wheels/tyres, 18" wheels/tyres and the Sagaris disc brakes.
I run 255/35 x 18 R1R's front and rear. I have raised my steering rack by 15mm also. This transformed the cars handling for the better. As did cranking in over 5 degrees of catsor to the front wheels and some rear toe in. I am still playing with it but I really do feel as though I am at last close to getting the best out of my Tuscan.
This does all depend of course upon ones preferred style of driving.
Also I am about to fit the MK1 "S" splitter but I will give it a 20 degree angle of attack towards the road surface, unlike all the others that I have seen which seem to be almost parallel with the road surface.
I have also now built a new 383ci SBChevrolet for it. Hope to post the dyno results tomorrow on my link. I have changed the rpm at which the torque comes in and paid a lot of attention to matching it to the clutch, a McLeod twin plate, and the ultimate rev range of the motor. It is about 526Bhp now @ about 6300rpm with 446ftlbs of torque at about I think from memory 5500Rpm, but as I say, dyno sheet maybe tomorrow.
I have been rebuilding this 383ci motor with John Sleath Racing.
Don't forget I am building a GT..... not a racing car.
Regards.
Speed eight.
Edited by Speed eight on Wednesday 4th May 18:10
Edited by Speed eight on Wednesday 4th May 18:11
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