speedo accurate

[beritz]

how accurate are the speedos in the griff
as i seem to be doing 90-100 and every one is still going past me how can i get this checked as i dont want to put my fragile driving licence under more strain

[simpo one]

From my experience with 3 TVRs they seem to be pretty accurate, not having the usual over-read of 'normal' cars. I don't know *how* I know that, it's just a feeling compared with other traffic.

Can you work it out from the rev counter and gear ratios? Or get a friend to drive with you at a known speed?

[shpub]

Go to www.tvrbooks.co.uk and download the tyre size spread sheet. This will work out speed vs revs for gear ratios and different tyre sizes.

Steve
www.tvrbooks.co.uk

[GarryM]

Does that mean the rev counter is accurate? I think my speedo' is a bit optimistic as well - what concerns me more is that if it is say 10 - 15% over the top I presume it means the mileage reading is 10 -15% OTT. That's a lot of miles.

Edited for spelling - doh!

>> Edited by GarryM on Monday 9th September 09:01

[steve-p]

If you really want a definitive answer, buy or borrow a GPS and use that for comparison purposes. My Griff underread by 2mph at 80mph, i.e. an indicated 80mph was 82mph.

[dan]

I'll have to check mine too.

I recon it's reading about 10mph out at motorway speeds, i.e reads 80 when I'm doing 70.

[tjasper]

I posted about this several weeks ago. Mine reads about 10% fast -that is 100mph is nearer 91mph. Checked it with the posts along the motorway and from the calculated rpm/gearing from Steve Heath.

Seems some of them do read optimistically, some accurately. I wonder if there were problems with the speedo drive units and sometimes the wrong ones got fitted?

Hope that helps,

TreVoR

[toffer]

Strange, checked my Griff speedo because I was unwilling to try and keep-up with one of my mates who was driving at 95 mph...
he told me his speedo said 80 mph!
I checked on the motorway posts and mine was spot on.
His car had been fiited with the wrong gear on the sender unit.

>> Edited by toffer on Wednesday 11th September 18:55

[GarryM]

quote:
I checked on the motorway posts and mine was spot on.

That sounds easier than finding a GPS - how far apart are the m'way posts? (am I the only one who doesn't know? )