Tyre Load & Speed Rating

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Tyre Load & Speed Rating

Postby sam355 on Wed, 27 Oct 2021 4:18 +0000

Hi,
Have a question regarding tyre load and speed rating:
If a tyre is rated 123K (Cooper SST Pro) does that mean at 123 max load (i.e. 1550 kg per tyre) the maximum speed should not exceed K (i.e.110 km/h), BUT as I`m planning to install these tyres on a SR5 (2080 kg + constant load of 300 kg), I will be way under the combined load rating of the tyres (6200 kg load rating vs actual 2380 kg) so going above 110 km/h say up to 140 km/h would not be an issue?!!!
Hard one for me to answer :geek: :lol:
Thanks,
Sam
sam355
 
Posts: 51
Joined: Thu, 19 Mar 2015 2:21 +0000
Location: Bexley, UK


 

Re: Tyre Load & Speed Rating

Postby sam355 on Wed, 27 Oct 2021 6:50 +0000

Response from Cooper UK:

Good morning Sam,

Thank you for contacting Cooper Tires with your enquiry.

The size of tyre you have enquired about is classified as a LT (Light Truck) design. Because of this is under European and UK legislation it is considered as a commercial tyre and has to conform to:-
UN Regulation 54 – Uniform provisions concerning the approval of pneumatic tyres for commercial vehicles and their trailers.

The Discoverer STT Pro P.O.R. range is exempt from some of the legislation required under UN Regulation 54 as it is classified as a P.O.R. (Professional Off-Road) To receive a P.O.R. rating any tyre with a load rating over 121 (you mentioned the tyre size you are considering has a load rating of 123) is required to have a maximum speed rating of K (110km/h - 68mph). Accordingly we can only recommend fitting tyres that meet the requirements as set out by the vehicle manufacturer, suitable fitments will be recorded on the placard mounted near or on the door of your vehicle.

We cannot recommend exceeding the speed limit of our product, regardless of vehicle loading.
Also it may fall foul of The Road Vehicle (Construction and Use) Regulations 1986, with the tyre being unsuitable for the use to which the vehicle is being put to.

If you have questions regarding this or need more information please contact your vehicle manufacturer.

Kind regards,
sam355
 
Posts: 51
Joined: Thu, 19 Mar 2015 2:21 +0000
Location: Bexley, UK

Re: Tyre Load & Speed Rating

Postby sam355 on Wed, 27 Oct 2021 10:08 +0000

Same tyres P rated on the USA Web Site so what Cooper UK mentioned makes sense:

https://coopertire.com/en-us/find-tires ... er-stt-pro
sam355
 
Posts: 51
Joined: Thu, 19 Mar 2015 2:21 +0000
Location: Bexley, UK

Re: Tyre Load & Speed Rating

Postby ravik on Thu, 17 Feb 2022 8:20 +0000

I'll soon be buying brand new Michelin Pilot Sport 4 tires for my e36 325i, I'm set on 225/45/17s (wheels are 8J). What load and speed index should I get?

I know the higher the load index, the heavier the car may be, but does that mean the highest load index is best? Or should I get the one that's right on the edge? Same for speed index.

I have the choice between 91V, 91W, 91ZR(Y), 94W & 94ZR(Y).

Thanks!
ravik
 
Posts: 1
Joined: Thu, 17 Feb 2022 6:06 +0000
Location: India


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