"Jittery" at Speed
Discussion
Had my T350C for 2 months now and apart from the usual minor niggles my main concern is how jittery and unstable the car is a high speed. If I go over 200kmph (128mph) the car becomes very scary - the car "tracks" the road and is all over the place - I've always considered myself to be a fairly gutsy guy but I get the feeling that if I were to take the car anywhere near it's top speed potential I would be in serious trouble. My mate has a T350c and reports the same problem. Is this an issue with all T350's and is their a Fix? I have tried various tyre pressures - harder tyres = problem worsens, I currently run the tyres with 190KPa all round - seems to offer the best compromise between handling and comfort. Any ideas anyone?
mwtryan said:
Had my T350C for 2 months now and apart from the usual minor niggles my main concern is how jittery and unstable the car is a high speed. If I go over 200kmph (128mph) the car becomes very scary - the car "tracks" the road and is all over the place - I've always considered myself to be a fairly gutsy guy but I get the feeling that if I were to take the car anywhere near it's top speed potential I would be in serious trouble. My mate has a T350c and reports the same problem. Is this an issue with all T350's and is their a Fix? I have tried various tyre pressures - harder tyres = problem worsens, I currently run the tyres with 190KPa all round - seems to offer the best compromise between handling and comfort. Any ideas anyone?
UK Cars run lower pressures than you indicate. If my conversions are correct, you currently run 28 psi. A UK car would run 24 front and rear - 160Kpa. Track day use the 24 PSI seems to work fine too.
The T350 does move around a little at speed, but shouldn't be that much of a concern. We've run ours up around 270kph for short periods without being too concerned about stability.
We were more concerned about trying to keep up with the RR Cerb in front.
If Daftlad's tyre pressure calculations are right then this is probably the cause of the jitteryness. I really high speed I find the car can be quite sensitive, but not jittery. Obviously if the road surface is not good then maybe I wouldn't be going too quick anyway.
24psi is plenty. Esp. since SA is a hot climate = even higher tyre pressures.
24psi is plenty. Esp. since SA is a hot climate = even higher tyre pressures.
OOPS! I said 190KPA, it is in fact 190BAR - Daftlad - perhaps this will make my tyre pressure more correct?
This is what the handbook recommends, although I have been told that due to the high altitude in JHB I could run 10BAR less. Our roads here are generally pretty appalling however the highways (motorways) are generally as good as Europe.
This is what the handbook recommends, although I have been told that due to the high altitude in JHB I could run 10BAR less. Our roads here are generally pretty appalling however the highways (motorways) are generally as good as Europe.
All too familier story!! I had the same problems and had to do something about it for my own safety. Dealer tried to sort it but in the end i changed to nitron shocks and eibach springs. Different car! feels very planted now not wandering all over the road. There are planty of previous threads on this if you do a search. I have heard a rumour that TVR will be changing the suspension set up on the new T350's to te same as the Sagaris.
mwtryan said:
OOPS! I said 190KPA, it is in fact 190BAR - Daftlad - perhaps this will make my tyre pressure more correct?
I dont think so....thats 2755 psi.
I suggest you try running at about 155 -160 KPA.
Prof Pat Pending said:
I have heard a rumour that TVR will be changing the suspension set up on the new T350's to the same as the Sagaris.
Bilstien shocks and Eibach springs in the very near future. No details on the finer points.mwtryan said:
OOPS! I said 190KPA, it is in fact 190BAR - Daftlad - perhaps this will make my tyre pressure more correct?
This is what the handbook recommends, although I have been told that due to the high altitude in JHB I could run 10BAR less. Our roads here are generally pretty appalling however the highways (motorways) are generally as good as Europe.
190bar
isn't that about 2800 psi?mwtryan said:
Thanks Prof. PP for the tip - however it's pretty annoying to find that you have to shell out for upgrades to the suspension in order to realise the car's true potential! Perhaps you can point me in the right direction as to where to purchase the springs & shocks?
Start by getting those tyre presures sorted, and if need be, a 4 wheel alignment.
Keep you Rand in your pocket for the time being.
groucho said:
OOPS! I said 190KPA, it is in fact 190BAR - Daftlad - perhaps this will make my tyre pressure more correct?
This is what the handbook recommends, although I have been told that due to the high altitude in JHB I could run 10BAR less. Our roads here are generally pretty appalling however the highways (motorways) are generally as good as Europe.
190bar
Sorry daftlad, I see you spotted it before.
Tim,
I agree you should explore all options before changing the suspension. As suggested tyre pressures and geometry are very important. if you do decide to change then ensure its done properly by someone who knows hat they are doing. Sorry cant help with details in SA but in the UK there are several places that can do the upgrades. I got mine done at Guglielmi Motorsport and was pleased with the results. I know other pher's have also used him. hope you get it sorted soon!
I agree you should explore all options before changing the suspension. As suggested tyre pressures and geometry are very important. if you do decide to change then ensure its done properly by someone who knows hat they are doing. Sorry cant help with details in SA but in the UK there are several places that can do the upgrades. I got mine done at Guglielmi Motorsport and was pleased with the results. I know other pher's have also used him. hope you get it sorted soon!
I was getting quite severe understeer on tight lock, a new experience in a TVR and I had the geometry and tyre pressures checked at Silverstone TVR. That solved the understeer (geometry was way out) but it still wanders around at speed. I'll uncertainly investigate the shocks and springs upgrade.
I had exactly the same issues. I was genuinely concerned about driving the car at speed, after driving mass produced vehicles much faster...
It's an 03. Took it back to the dealer and had the Geometry set to the latest factory settings, and they also raised the suspension slightly. Now it's much better, I have more confidence in the car. That said, I'd still consider shocks and springs if it would eliminate it toally. Whats the cost like?
It's an 03. Took it back to the dealer and had the Geometry set to the latest factory settings, and they also raised the suspension slightly. Now it's much better, I have more confidence in the car. That said, I'd still consider shocks and springs if it would eliminate it toally. Whats the cost like?
Just a quick heads up!
Nitrons are about 1K but then you need to get them fitted. Then you need to think about whethr you upgrade the springs or stick to the originals. new springs plus fitting/geometry take this over the £1500 mark.
results are good but not remarkable. Ie as is on the crappy UK roads 6/10ths goes to 8/10ths but better on smooth track!! You will never be able to get that mass produced planted feel like the Porsche but the handling is a great improvement!
Nitrons are about 1K but then you need to get them fitted. Then you need to think about whethr you upgrade the springs or stick to the originals. new springs plus fitting/geometry take this over the £1500 mark.
results are good but not remarkable. Ie as is on the crappy UK roads 6/10ths goes to 8/10ths but better on smooth track!! You will never be able to get that mass produced planted feel like the Porsche but the handling is a great improvement!
OOPS - AGAIN! Blimey - don't I feel like a wally! Regarding tyre pressure - youre all quite right of course - went to my local garage and checked - SA pressure meters are measured in BAR - but my pressure was not 190 as previously stated - but 1.9BAR - silly me was reading the guage wrong thinking 1.9 was 190!
At least I now know I have not been overinflating the tyres.
Quickly popped round to TVR who suggested lowering the pressure to 1.8BAR - duly did this and off I went - not much improvement I must admit - understeer and wandering still at lethal levels - my previous Chim 500 was soooo much more stable at high speed - hope I don't meet any AMGs, BM's or Porsches on the highway anytime soon as I will definately see my A#*e! Pity really as one of my favourite previous pastimes was running away from the Germans in the Chim from 200kmh!
I also popped in to my local friendly tyre speialists who tried to check for alignment - more bad news - due to the car's low design the local alignment machine could not be correctly fitted to the car - however they reckon that changing the camber of the wheels to offer more of a "racing" set-up might help - down side being quicker tyre wear - now being no expert perhaps someone in the forum could shed some light on this?
At least I now know I have not been overinflating the tyres.
Quickly popped round to TVR who suggested lowering the pressure to 1.8BAR - duly did this and off I went - not much improvement I must admit - understeer and wandering still at lethal levels - my previous Chim 500 was soooo much more stable at high speed - hope I don't meet any AMGs, BM's or Porsches on the highway anytime soon as I will definately see my A#*e! Pity really as one of my favourite previous pastimes was running away from the Germans in the Chim from 200kmh!
I also popped in to my local friendly tyre speialists who tried to check for alignment - more bad news - due to the car's low design the local alignment machine could not be correctly fitted to the car - however they reckon that changing the camber of the wheels to offer more of a "racing" set-up might help - down side being quicker tyre wear - now being no expert perhaps someone in the forum could shed some light on this?
mwtryan said:
OOPS - AGAIN! Blimey - don't I feel like a wally! Regarding tyre pressure - youre all quite right of course - went to my local garage and checked - SA pressure meters are measured in BAR - but my pressure was not 190 as previously stated - but 1.9BAR - silly me was reading the guage wrong thinking 1.9 was 190!
At least I now know I have not been overinflating the tyres.
Quickly popped round to TVR who suggested lowering the pressure to 1.8BAR - duly did this and off I went - not much improvement I must admit - understeer and wandering still at lethal levels - my previous Chim 500 was soooo much more stable at high speed - hope I don't meet any AMGs, BM's or Porsches on the highway anytime soon as I will definately see my A#*e! Pity really as one of my favourite previous pastimes was running away from the Germans in the Chim from 200kmh!
I also popped in to my local friendly tyre speialists who tried to check for alignment - more bad news - due to the car's low design the local alignment machine could not be correctly fitted to the car - however they reckon that changing the camber of the wheels to offer more of a "racing" set-up might help - down side being quicker tyre wear - now being no expert perhaps someone in the forum could shed some light on this?
1.8 bar is too high. 1.6 bar (160 kpa) is where they should be.
Springs and shock change will not by them self cure the pervceived stability issue unless there is a problem with the original equipment.
I would take advice from someone other than your local tyre dealer - hes not got a clue by the sound of it
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