Speedo reading in GT3..
Discussion
My GT3 speedo over-reads according to my GPS device by approximately 5/6%. Is this normal?
I've noticed my girlfriend's father's X5 over reads according to his GPS too, and know it's to be expected at high speeds but, when pootling along at say 100 elephants an hour according to the speedo, the GPS is reading about 95 eph.
I therefore get shouted at by the gf when she looks across, sees the speed reading starting with a `1` and get told to slow down or i'll lose my license.
My old C5 was absolutely spot on against the (same) GPS device all the way up to 168eph.
I don't like me car lying to me - I want to know what speed I am actually doing, not what Porsche applying some safety margin are telling me i'm doing..
I've noticed my girlfriend's father's X5 over reads according to his GPS too, and know it's to be expected at high speeds but, when pootling along at say 100 elephants an hour according to the speedo, the GPS is reading about 95 eph.
I therefore get shouted at by the gf when she looks across, sees the speed reading starting with a `1` and get told to slow down or i'll lose my license.
My old C5 was absolutely spot on against the (same) GPS device all the way up to 168eph.
I don't like me car lying to me - I want to know what speed I am actually doing, not what Porsche applying some safety margin are telling me i'm doing..
A 7% over-reading is not abnormal for any car and Porsches are not immune to this. I believe that the manufacturers are under some sort of (legal?) obligation to make sure that your speedo over-reads as opposed to under-reads as this should help to keep you out of trouble.
Consider the variables such as tyre pressure and tread depth....
When tyres are new the tread depth is often 8mm. After you have worn them down to the legal limit the circumference (C = 2 x PI x R remember!) and therefore final gearing, will be reduced by apprx 3%.
Consider the variables such as tyre pressure and tread depth....
When tyres are new the tread depth is often 8mm. After you have worn them down to the legal limit the circumference (C = 2 x PI x R remember!) and therefore final gearing, will be reduced by apprx 3%.
I thought my 996 C2 3.6 was running 5% high but after a bit of testing it works out that it overreads by 5mph over the whole speed range - I've tested at a constant 30, 100 and 150mph so far and it is always 5mph rather than 5%
Tested against TT navigator and Snooper s6 which were both reading the same speeds.
Cheers
Paul
Tested against TT navigator and Snooper s6 which were both reading the same speeds.
Cheers
Paul
vette78 said:
I therefore get shouted at by the gf when she looks across, sees the speed reading starting with a `1` and get told to slow down or i'll lose my license.
domster said:
I'd be more worried why your car's not reading in mph
I'd be even more worried about your choice of girlfriend
!!!slippydiff said:
vette78 said:
I therefore get shouted at by the gf when she looks across, sees the speed reading starting with a `1` and get told to slow down or i'll lose my license.
domster said:
I'd be more worried why your car's not reading in mph
I'd be even more worried about your choice of girlfriend
!!!Haha, don't worry - it's my license she's mainly concerned about which is better than being a general shouter of `SLOW DOWN`. In france she was the one keeping an eye on the GPS speed whilst I kept an eye on the road...
Seems like it is normal then. Can't say I like it, especially as i think mine may well be about 5 mph over the whole range as with one of the previous posters. Showing 35 at 30 is too much.
I like some of the ridiculous over-reading stories though - 210mph in a Tuscan - it would rip apart!
vette78 said:
slippydiff said:
vette78 said:
I therefore get shouted at by the gf when she looks across, sees the speed reading starting with a `1` and get told to slow down or i'll lose my license.
domster said:
I'd be more worried why your car's not reading in mph
I'd be even more worried about your choice of girlfriend
!!!Haha, don't worry - it's my license she's mainly concerned about which is better than being a general shouter of `SLOW DOWN`. In france she was the one keeping an eye on the GPS speed whilst I kept an eye on the road...
You should have seen the look on my wifes face during the high speed convoy to the 'ring whilst following 6 other GT3's
Not happy with the new finger holes in my dash tho
Don't forget that GPS - as my little brain understands it! - measures speed over the earths surface and it assumes that the earths surface is a constant radius so if your speedo is showing 100mph but you're going up a very steep hill the GPS will show your speed as slightly less as it won't allow for the fact that you're going 'up' as well as across the surface of the earth. Er, I think!
Gassing Station | Porsche General | Top of Page | What's New | My Stuff