Just wondering.

Additional point - Tyres will only ever be used in a straight line - quarter mile at a time.

So, are tyre speed ratings generally done for "all conditions" including cornering etc? I am wondering how an "M" rated (officially around 80mph I think) tyre will be on the back of a car at 110mph odd....

Any thoughts? There must be people using skinny back wheels on ultra fast front wheel drive cars?

They will instantly explode and send you back in time, thus impairing your terminal speed and 1/4 mile time as you will finish before you started.

They will instantly explode and send you back in time, thus impairing your terminal speed and 1/4 mile time as you will finish before you started.

Bonus! If the laws of quantum physics are the only thing I risk breaking, then so be it.

The speed rating is a maximum continious speed.

Why would you want to fit skinny wheels on the back of a front wheel dive car.

I cant think of any benifit.

Drag racing a FWD car, skinny tyres on the back will have less rolling resistance.

The speed rating is a maximum continious speed.

Why would you want to fit skinny wheels on the back of a front wheel dive car.

I cant think of any benifit.

Less rolling resistance = Quicker

They do have an influence on the acceleration and braking loads you can safely apply, as does the vehicle weight. What sort of ET and TV are you expecting?

Less rolling resistance = Quicker

Just pump the existing ones up to 80psi.

Come on Jason, with the latest modifications you're not going to have to go this far to beat my 13.6 time...

I'm still keeping mine road standard with the seats and spare.

Just wondering.

Additional point - Tyres will only ever be used in a straight line - quarter mile at a time.

So, are tyre speed ratings generally done for "all conditions" including cornering etc? I am wondering how an "M" rated (officially around 80mph I think) tyre will be on the back of a car at 110mph odd....

Any thoughts? There must be people using skinny back wheels on ultra fast front wheel drive cars?

I believe it certifies that the tyre can handle that speed in a straight line for a 10 minute burst. So buy good quality M rated tyres and you'll probably be fine for a few second burst at 80mph+. Then cooling down while you wait to run again. Buy ditchfinders and you'll have less grip/rolling resistance, but they might explode as soon as you hit 80.1

edit -

The tyre speed rating (i.e. S) is the maximum speed for which the tyre is rated. For example, the S rating identifies speeds up to 112 mph.

Speed ratings are based on scientific tests where the tyre is run at speeds in 6.2 mph steps in 10 minute increments until the required speed has been met.

It's not 100% clear from that whether it means "test tyre in 10km/h increments until it fails, and then sell it as the last figure it achieved", or "test tyre in 10km/h up to target speed and make sure it gets there". If it's the first one, then there's barely any leeway over the rated figure, if it's the second then it could be that tyres are capable of much more than the rated figure but haven't been tested.

Edited 2 December, 201114 yr by gac

Yes you should be fine.

Our recent trip to Germany saw us driving at 120mph for most of the time then I drove at top speed for several miles (138mph gps). It wasn't until afterwards that it dawned on me that the tyres are H rated.

Phil

Ah, cool. Yes, I shall only be above 80mph for about 5 seconds I think. In that time it takes me to go from 80mph to 110mph and over the 1/4 mile line, then back down gently to normal speeds.

I am hoping for 110mph terminal speeds over the 1/4 mile, circa 13 seconds flat. I've already done 105mph terminals @ 13.7 with shocking starts off the line (with alloys on the back). I'm also a gearchange down now too with the longer ratio box. 4th gear should be 115mph @ 4,500rpm which is perfect for a 1/4. With the space savers on there will be no cornering at even anything slightly "fast". Straight line only.

If only I could master 2nd gear starts. Would only need 2 gear changes for the whole 1/4 then...

I believe it certifies that the tyre can handle that speed in a straight line for a 10 minute burst...

Correct, but in practice you will find that car manufacturers specify a speed rating one step above what would seem to be required. If you look in the speed rating table you will find test speed - not the recommended speed for any particular vehicle.

It is generally accepted that one speed rating above that calculated from the maximum of the speed of the car, is good for the continuous maximum speed of the car in a straight line under the specified load rating. So for a car to be 'fully provisioned' you need to go with the manufacturer's recommendation or look at the rating for the maximum speed of the car and go up one rating.

If you have different speed ratings on the front and rear, you would normally put the lower speed-rated tyres on the front axle to help prevent oversteer - regardless of which axle is the drive axle.

Dragging a car will have little impact on the rear tyres, they will never get hot enough to fail, whatever the speed rating (within reason!)

As said, pumping them to a high PSI to run on a small centre peice of tread will acheive the same thing. Although of course smaller wheels and tyres are lighter.....

Also, re speed ratings on the strip the fronts could be sub 20psi which will effectivly take chunks out of any manufacturer speed ratings.

2nd gear starts are the way forward

J

A change of direction Jason? Surely you are not giving up trackdays. You need some super soft track tyres for the front but anything that supports the rear end will be sufficient, just don't drive on the road with pram wheels though :wonder:

Change of direction? Absolutely not. It will still be a trackday fun car, daily driver and "hopefully" a 12 second quarter mile car... We shall see.

Oh good, you had me worried there.

Oh good, you had me worried there.

I think I might use 17" alloys all round for the trackdays though.

Probably a good idea Jason.

1st. track day for me in the Westfield a couple of weeks ago, WOOOOOW!

Ok, I suspect the reduction in reciprocating mass will make more of a difference to the ET than the reduction in tyre drag will. I'd be a bit ginger in braking until I knew what the stability was like though.

I only ever "coast" if you like, in gear, and brake just at the end. I never fancy putting the anchors on at 105

Not tried a second gear start yet either. Heard that it can help greatly as although you initially don't get off the line quicker you don't run out of revs on the short first gear and save a gear change.

Might have to have a play some time now that I have my need engine mount fitted

Nice times BTW Jason. Not bad for a pd100