Tracking on 280i
Discussion
I haven't got the figures to hand but the tyre size is a bit too wide for the rim and will suffer from tread roll over where the sidewall starts to lift the tyre up off the road. The normal practice is to increase the tyre pressure but this balloons the tyre and makes the problem worse. So you get into a catch 22 situation where you need to run a higher pressure to stabilise the tyre sidewall but this reduces the contact patch and grip.
In extreme cases, the tyre can roll under the rim and the sidewall makes contact with the road. Didn't believe it until I saw I had worn the sidewall lettering. I would start at around 24 lb and start experimenting.
Steve
In extreme cases, the tyre can roll under the rim and the sidewall makes contact with the road. Didn't believe it until I saw I had worn the sidewall lettering. I would start at around 24 lb and start experimenting.
Steve
The tyres are on 390SE wheels which are wider than the standard 280i ones and allow for a lower profile tyre.
Although the tyres and rims are wider, the overall diameter is exactly the same as standard spec.
I believe the tyres are the correct size for the wheels.
Does this sound OK to you Steve?
Although the tyres and rims are wider, the overall diameter is exactly the same as standard spec.
I believe the tyres are the correct size for the wheels.
Does this sound OK to you Steve?
Not really as it was on my 390SE in standard trim that I and others hit the problem. TVR specified the 225/50 tyre as an after thought and didn't increase the wheel size as a result. It is OK on a 8J or a 7.5 but most of the 390SE were a 7J where the original spec tyres of a 215 or 205 were fine but the 225 pushed it over the limit. So it all depends on the wheel width.
It is fine for poodling about but when pushed really does start causing some very interesting handling. Like driving on a blob of silicone rubber interesting.
For the later nutter cars, TVR started to fit wider wheels to complement the tyre size better.
Steve
It is fine for poodling about but when pushed really does start causing some very interesting handling. Like driving on a blob of silicone rubber interesting.
For the later nutter cars, TVR started to fit wider wheels to complement the tyre size better.
Steve
quote:
My 350 with std wheels has 205 60 15 tyres on at the moment, Can I therefore put on 215 50 15 's on it and recalibrate the speedo? It doesn't have a lot of ground clearence as it is, is this a problem?
There is a tyre size/speedo calculator spread sheet on my web site that will calculate the differences in circumference, diameter and speedo readings. Probbaly not worth recalibrating as the speedo is not that accurate anyway and I think the difference is only a few % anyway.
Steve
My 390 does suffer from a bit of tramlining, as did the Tasmin, but since steering that was akin to directing a supertanker with a canoe paddle over the side, it wasn't much of a problem!
Can't say I drive in a gung-ho-enough fashion to have the wheels rolling over the sidewalls; usually I find the arse end (mine as well as the car's!) has let go long before the front gives me trouble.
At a quick guesstimate, I'd have said that the difference in ground clearance between the two tyre sizes mentioned would be negigible!
W.
Can't say I drive in a gung-ho-enough fashion to have the wheels rolling over the sidewalls; usually I find the arse end (mine as well as the car's!) has let go long before the front gives me trouble.
At a quick guesstimate, I'd have said that the difference in ground clearance between the two tyre sizes mentioned would be negigible!
W.
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