Smaller wheels and speedo

[Impey]

When changing to smaller wheels are you go faster or slower by the speedo?

 

[480bhp.com]

Faster on the speedo, slower in reality

Chris

 

[Jamesyy]

Does that mean changing to bigger wheels would make you go faster in reality but slower on the spedo then?

 

[rory182]

larger wheels = slower acceleration and higher speed but speedo will under read
smaller wheels = faster acceleration and lower speed but speedo will over read

There's sites which allow you to compare original tyre size with new tyre size and it tells you by what % the speedo will read over or under by:

http://www.paspeedo.com/calculator.htm

 

[Nick_P]

My car tells me im doing 50 and im doing 55, i have 16's on but it shouldnt be doing this tooo meeee

 

[Jamesyy]

cheers mate

 

[rory182]

cheers mate

experiment with different tyre profiles you may be able to change wheel size without affecting the speedo too much e,g, 1-2% difference

 

[DrR]

my 15"s underead

 

[Ben^]

its all based on your rolling radius and if you up the wheel size and lower the tyre size correctly and visa versa and within reason you shouldn't notice any real difference.

Example - My 172 has 16" wheels with 195/45/16 tyres, if I was to reduce the size to 15" then I would probably fit 205/50/15 tyres which only changed the speedo reading by 0.7%. All be it there a little wider but unless ur car is 60mm down on stock u should be ok, can always remove arch liners .

http://www.kouki.co.uk/utilities/vis...ize-calculator

that should give you a good indication of what sizes you can use whilst keeping the speedo reading as normal as possible.

 

[BIFCAIDS]

my old (standard wheels) have a bigger tyre on them than my new wheels and im reading 30 on clock but 27/28. this is all gestamates anyway because whats to say your speedo isnt out anyway? just dont do 30 threw a camera do a little less, thats what i do because i play it say