speedo and tyre width?

[Jcerb]

Is the speedo taken off the gearbox or somewhere else? Also as i want to keep same rolling radius as standard saturns on a 4.2, you cannot get 225/40/17's(same rr as 225/45/16) anymore. Will 235/40/17's tramline?? or rub on full lock being that much wider. Thanks guys if anyone has tried this.

[RichV6]

Running 235 40 17's on my 4.2 on standard 17"RL's. With Toyo T1R's
theres no tramlining or rubbing.

The speedo is electronic, the pickup being on the diff output flange.
In my case the speedo is within 1 mph at 70mph measured by GPS.
The car is on 17" wheels and standard spec Cerb 4.5 tyres

[Jcerb]

Hi Richv6, thanks for that, very helpful. What are you running on the rear? 245/40/17's?

[RichV6]

I'm not at home until next week but I think they are 255 40 17's. I'm
sure those running standard 4.5 wheels will confirm if this is correct

[grahamn]

RichV6 said:

I'm not at home until next week but I think they are 255 40 17's. I'm
sure those running standard 4.5 wheels will confirm if this is correct