Larger tyres - Speedo error?

kernowdragon

Well-Known Member

Posts

1,918

Location

Wickford, Essex

• Apr 20, 2010

• #1

OK, so I know a speedo can never under read, and can over read by up to 10%, but I'm thinking of switching My RR's standard 255x65/16's for Cooper ST's in 265x70/16, which according to the specs means a speed increase of 4.9% over the originals. Question is... is this likely to be enough to put me over when it comes to the MOT?? Does anyone have experience of this switch, or others that have resulted in a similar increase, and how did they fare with the tester??

 

Paul D

Old, nackered 'n broke, but the Landy is fine . :)

Events Planner

Posts

14,902

Location

Doncaster

• Apr 20, 2010

• #2

I went to larger tyres and the Disco now reads bang on at 70 ..

Speedo accuracy is not an MOT test ... only a speed camera test ..

 

storm99

Spreading Joy & Harmony

Posts

21,065

Location

Brexited. Living on an island.

• Apr 20, 2010

• #3

I drive past 3 ''your speed is'' electronic signs..and they all say i'm doing 10% more than my speedo..45 when speedo says 40, 55 at 50mph...running 235/85/r16's..

 

jai_landrover

Well-Known Member

Posts

13,392

Location

Luton

• Apr 20, 2010

• #4

I wouldn't worry the difference is minimal in rolling circumference TBH the speedo may read a couple of Mph different nothing to worry about.

 

hughesy

Well-Known Member

Posts

4,200

Location

Isle of Anglesey

• Apr 20, 2010

• #5

If it bothers you check your speed with a sat nav then you'll know how accurate it is.

 

kernowdragon

Well-Known Member

Posts

1,918

Location

Wickford, Essex

• Apr 20, 2010

• #6

Cheers, chaps! I'd assumed they checked the speedo while they had it on the rollers. If not then there's no problem, once I know from the satnav whats what it'll be fine.