Due to indicated speeds I was entertaining the idea that possibly my car had a N/A diff. But, seeing as my car has HICAS, surely that confirms it is a TT diff? At 4k rpm my speedo shows just under 100mph - which is what lead me to believe that it was a N/A diff. I'm thinking its more likely to be a speedo discrepency? Which means I'm probably going a little quicker than I actually think?

 

Am I right that only the TT diff has HICAS?

 

Cheers

i believe you are, however its probally related to your tyre size. plus havent you just had a rebuild, with some tricks? so likley the engine will be working less to achive the same speed.

Wheels are 17" jobbies, with 235 45 section tyres - so I was thinking that they'd be pretty much bob-on size wise. Anyone else running 17's with a slight speedo innaccuracy?

use this find out.. :D

http://www.miata.net/garage/tirecalc.html

NA diff means NA subframe which means no HICAS im pretty sure

That looks very handy! If only I knew the stock wheel dimensions!

 

Off to do some digging...

16x50x225

Rears on a uk car are 245/45/16

Difference between my wheels and stock items is less than 2 % of overall rolling diameter - which still doesn't explain the near 8% descrepency on the speedo at 4k rpm in 5th. Must be something else I think?

use your sat nav speed indicator to see how far your speed is out ...

as far as i'm aware your speed so should be spot on at 50mph then should drift out a little after

clock 73mph should be 70mph real speed ...

Edited August 29, 201114 yr by MarkDerby

Its possible you could have the leader 4.1 gears in TT Housing.

 

But have you checked speed with GPS. The Stock Speedo is far from reliable, and most cars are often anything up to 10% (or more) inaccurate anyway

Edited August 29, 201114 yr by Yowser

I'm old school - I don't have Sat Nav.. I prefer to know where I'm going before I get there!!

 

That said, I could borrow one - will let you know in a few weeks.

You have a stock 95 rear subframe matey with electric hicas as it should be.