Tyre load and speed indexes

DB_SamX

DB_SamX

DB_SamX

Soldato
Joined
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I've never given it thought before or checked, but to what extent does the load and speed indexes matter when it comes to performance/handling but more importantly MOT/insurance, if at all?

Do your car manuals advise on any minimum and recommended values in each case?

In my case, just been looking at replacement tyres for the Celica and noticed that for 205/45/17, CSC3 are either £115 a corner for 88W or £99 for 84V. From Blackcircle, the difference is max top speed of 168mph(W) vs 149mph(V) and 560kg(88) vs 500kg(84). Speed is well within limits for non-track use and you'd only really hit 2 tons in the car, if you had 4 obese people in there and the boot equally filled.

My manual doesn't advise any minimums but its recommended tyre pressures are based on the 88W.

Does everyone stick religiously to the numbers?
 
The higher the load rating the crisper the turn in you get but you sacrifice some ride comfort.

For example most of the Honda DC5 boys use XL side-walled tyres which are rated to 94 or something as it gives better handling despite it being only an 1100kg car.

As for speed rating, it needs to be rated to the cars potential speed, not the speed you intend to do. So if you car can nudge over 149mph you need the next rating up even if you never intend to go over 70mph.

Thats my understanding anyway.
 
In this instance, I would say it doesn't matter. You aren't going to be doing either of those speeds day to day. So if price if is your driver, go for the cost option.
 
Just out of interest, I popped by a local Toyota dealership this morning and they had no qualms recommending either 84W or 88W rated tyres.

Fyi, CSC3 were £148 fitted/balanced for 88W and £166 for 84W. Edit: latter is runflat hence more expensive.
 
Last edited:
sovietspybob said:
The higher the load rating the crisper the turn in you get but you sacrifice some ride comfort.

For example most of the Honda DC5 boys use XL side-walled tyres which are rated to 94 or something as it gives better handling despite it being only an 1100kg car.

As for speed rating, it needs to be rated to the cars potential speed, not the speed you intend to do. So if you car can nudge over 149mph you need the next rating up even if you never intend to go over 70mph.

Thats my understanding anyway.
Click to expand...

Speed rating is the speed the tyre can maintain for 10 minutes without self destruction taking place, so it is not critical unless you use autobahns or tracks :)

Load index is the load lugging ability upto around 200km/h, 210 I think, load index should be vehicle kerb weight/4 +20% for safety sake.

Exceeding load index will make the sidewall stiffer as a rule, and this can make the car more unpleasant over bumpy roads with little gain in performance if any.
 
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