Tyre Load Index and low weight cars
Discussion
This may have come up before. I am building a lightweight car (circa 450kg) and am investigating tyres. There seem to be plenty around at the higher load index (i.e. 88 and above) but none at the lower end.
AS the car is so light I am wondering if anyone has had problems with running significantly higher index tyres than is necessary. I've got no plans to go racing. It will just be for road use. Just want to make sure I have a sensible amount of grip
AS the car is so light I am wondering if anyone has had problems with running significantly higher index tyres than is necessary. I've got no plans to go racing. It will just be for road use. Just want to make sure I have a sensible amount of grip
Probably a bit different but I ran some high load tyres on my beach buggy which was bout 600kg but 70-80% at the back (think 102 load on the back), they only way to get it to ride well was to drop the pressures so that there was about 5mm bulge at the bottom of the tyre, this equated to about 16-18psi at the back, on the front I had some 82 load tyres, these had to run at 12psi.
It was always a bit of a compromise for bounce against ride harshness, and the weight distribution was an absolute nightmare in the wet.
It was always a bit of a compromise for bounce against ride harshness, and the weight distribution was an absolute nightmare in the wet.
That is the concern I think. My current plan was to use Toyo T1-R, the two fronts having 205/45/17", and the single rear being 275/40/18". You probably guessed this is a trike.
I have heard though that the compound might be a bit hard so I would have to drop pressure. The other possibility being to go to Proxes R888s which have a softer compound (althought they are a bit pricier.
As I am only going for road use I wasn't sure whether these would be too much
I have heard though that the compound might be a bit hard so I would have to drop pressure. The other possibility being to go to Proxes R888s which have a softer compound (althought they are a bit pricier.
As I am only going for road use I wasn't sure whether these would be too much
I think you will have limited tyre choice anyway due to the large sizes, so traditional " lightweight kitcar " tyres are only really in 13, 14 and 15". But whatever you end up with you will be fine and have to run low pressures ie: sub 20 psi or your contact patch will be so small and the ride rock hard. I'd suggest just seeking out the softest compound tyres possible of you may struggle to get any heat in them. Good luck!
PaulKemp said:
What worries me is that you have enormous tyres on a very light car sorry trike, that can only exacerbate your problems
As for load rating get the lowest you can find just make sure the speed rating is ok for your projected top speed
Thanks Paul. The top speed will be fairly low. This is being built just for the pleasure of building and driving. I have no intention of taking it to track days or spending my time whipping round country lanes.As for load rating get the lowest you can find just make sure the speed rating is ok for your projected top speed
It is interesting to hear all the comments as I certainly thought this would be the most challenging part of the selection process. The designer has put Toyo Proxes R888 on which appears to give good grip (certainly good enough for me). That is probably the fallback solution if I can't find anything else (just have to put up with the cost).
Now the Razor is a nice car, i would love to see and drive one. As for tyres, i had 888s on my atom and they are one of the best track tyres for lightweight car you can buy along with Yokohama AO48s. Unfortunatly these have very stif sidewalls so give a very harsh ride. Perfect for track use but can be a bit much for the road. I changed to the AD08 as these are more road friendly, about half the price and last a lot longer. If you are not tracking your car then you will not need 888s or AO48s
Mr2Mike said:
Complete and utter rubbish. I have used T1Rs on numerous different cars and lack of grip has never been an issue, wet or dry. The soft sidewalls are the main problem when fitted to heavy cars.
I've had T1Rs on a light weight car and didn't like them. At first I said they were rubbish and had no grip, then I went on a track day and after the fist lap or two they were fine. You have to get plenty of heat into them to make them work. Light weight cars just don't do that on the road. The glowing reports I'd heard from them were always when used on heavier machines which worked the tyres more.Derek, be careful not to over tyre your trike. You want the tyre to slip sideways before the trike starts to tip...
ALL vehicles will tip if your tyres are good enough. It's just a matter of how hard you can corner. I don't know what experience you have of trike driving. Having been through the learning experience, I'd recommend fitting OK tyres for the first year or so then putting better ones on when you're used to trike handling.
It better to slide than to tip and let's not even contemplate a tip!
ALL vehicles will tip if your tyres are good enough. It's just a matter of how hard you can corner. I don't know what experience you have of trike driving. Having been through the learning experience, I'd recommend fitting OK tyres for the first year or so then putting better ones on when you're used to trike handling.
It better to slide than to tip and let's not even contemplate a tip!
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