Speedo reading 15 mph out (approximately)

[Martin.p]

My speedo is out, 10-15 mph at what should be/ about 30mph.

thing is there calibra/cav clocks. Using a F20 on a C20LET.
Obviously the calibra had bigger wheels than what I'm using. (195/50/15)

is is there anyway I can change what the clock reads? (Other than fitting bigger wheels?, that wouldn't fit!)

or am I just going to have to get different clocks?

[andy_mk3]

I run those size tyres on my astra with an F28, speedo is spot on. Wouldn't have thought different clocks would read any different would they?

[Will F]

It shouldn't be that far out. Standard radius was 55 profile, so it's negligible...

[Martin.p]

Well, I was following a old couple through a 30mph zone. And passed one of them sines that flash 30 at you. And it didn't flash. And I was doing 43-45 mph. ( by my clocks.)

guess I'm going to have to get a mate to follow/follow me and be sure.

It's a mechanical speedo (if that makes any difference)

[Will F]

Lol that's how you've deduced your speedo is out?! Get a sat nav and check! Those signs don't even register most times you pass them

[Rage]

yep sat nav, talex, snooper or mobile app those signs always flash me when i know im doing 25mph yet they rarely flash at 31-32mph so their realy not reliable to judge your speedo

[Martin.p]

Hadn't thought of a sat nav. Will try that.

but, no. I'm not just basing it on one sine check thing. Most of the time you don't drive by looking into your clocks every sec. But quite a few times I've looked down and thought its reading more than it seems we're doing. Which tbh in a small car with all the road/engine noise it normally 'feels' faster than your actually going.
And the mi seem to be racking up a bit quick.

defo check it out to be sure. Reassuring to here others say it should be fine (as it is in there's)

[Martin.p]

Today I checked speedo reading against sat nav and it is 15mph out at 30 and 18-20 out at 60&70.

But it I think I know why.
Before I put the clocks in I took them apart and took the needle off and cleaned the orange pain of back
to get this look
http://i992.photobucket.com/albums/af46/martinstu/E6DD6F4D-54D6-4C51-B2E6-A4DA60DB7855-881-000000D9355EF8F6.jpg (http://s992.photobucket.com/user/martinstu/media/E6DD6F4D-54D6-4C51-B2E6-A4DA60DB7855-881-000000D9355EF8F6.jpg.html)

http://i992.photobucket.com/albums/af46/martinstu/702CC413-9642-4A8E-8041-F94961E1244D-3834-000004A580F8FB01.jpg (http://s992.photobucket.com/user/martinstu/media/702CC413-9642-4A8E-8041-F94961E1244D-3834-000004A580F8FB01.jpg.html)

i guess the spindle was slightly pre loaded when at 0.
Meaning I should of put the needle on at -15mph so to speak.