What have you done to your car today?

[Akagi]

Rust dipped stuff all painted up, and front crossmember stuff painted too...

Rockers and shafts out so I can get started on the stem seals...

 

[Rroff]

As in if you're doing 30 you're actually doing 26. This is pretty common on analogue dial cluster cars. It's usually a given it's around 3-4 secs out.

Every car I've had I've always gone up an inch or two on wheel size and fitted wider wheels/tyres with a lower profile. The speedo has always continued to read under, as I purposely have checked this, even when I've run taller profile really wide tyres and rims, like going from a 7.5J to a 9.5-10J, it still has red under.

It maybe different on newer cars with digital tachos/calibration, but wasn't the case for anything I've ever built/tested/driven, they have all red the same 3-4MPH real world difference, in my favour.

It varies depending on the car, but all 5 of my E36's for example have been 3-4 MPH out in my favour, and all 4 of my Honda's have been the same, as have any of my mates E28/34/36/38/39 BMW's.

I've driven a lot of older cars and none that are older have ever been 1:1 with a gps/satnav, always said it was going faster than it was.

I know on newer cars you can recalibrate the digital tacho if you change wheels/tyre size.

I don't think it's sus at all, and I'm reasonably sure that is 1 of the reasons the 1-3mph leeway existed, as there is a variance on old cars.

According to GPS and the digital signage they have up from time to time in the villages around here on standard size wheels/tyres my vehicles (less than 10 years old) usually over read by ~2MPH on the speedometer, depending a bit on the speed. The AT set I have for my pickup push it out by about 3-4MPH and same, the other way, when the dealer put it on wrong size tyres

 

[Removed User 345456]

According to GPS and the digital signage they have up from time to time in the villages around here on standard size wheels/tyres my vehicles (less than 10 years old) usually over read by ~2MPH on the speedometer, depending a bit on the speed. The AT set I have for my pickup push it out by about 3-4MPH and same, the other way, when the dealer put it on wrong size tyres

Do you mean in your favour? As in it says 30, and you're doing 26 or 28? Like my experience with older cars?

 

[Rroff]

Do you mean in your favour? As in it says 30, and you're doing 26 or 28? Like my experience with older cars?

Yeah if speedo says 30 and I go past one of the speed monitoring sign thingies in one of the villages it will say 28. I've got a GPS HUD thing, don't use it much as it poorly adjusts for light levels, and same for that.

 

[Uther]

Our new car with a digital dash reads 32 mph at 30 GPS. I assume that's pretty standard as it gives a bit of leeway.

 

[Removed User 345456]

Yeah if speedo says 30 and I go past one of the speed monitoring sign thingies in one of the villages it will say 28. I've got a GPS HUD thing, don't use it much as it poorly adjusts for light levels, and same for that.

Thought so, even changing wheels to bigger/wide ones with accompaning tyres has never made it a risk for me (ie under reading).
It'd only stitch you up if you ran smaller lighter wheels/tyres, due to less rotational mass, that's what I was trying to explain to @LuckyBenski

Uther:
Our new car with a digital dash reads 32 mph at 30 GPS. I assume that's pretty standard as it gives a bit of leeway.

Yep.

I've driven stupid amounts of new and old cars over the years in the motortrade, and I've never seen either old/new under-read, nor when modified with different bigger wheels.

 

[Rroff]

It'd only stitch you up if you ran smaller lighter wheels/tyres, due to less rotational mass, that's what I was trying to explain to @LuckyBenski

EDIT: Actually I think it is the other way around. Depending a bit on how your vehicle calculates road speed.

 

[Removed User 345456]

EDIT: Actually I think it is the other way around. Depending a bit on how your vehicle calculates road speed.

Check it with your phones GPS/dedicated satnav and compare it to the local speed trap readout and your dial cluster.
I genuinely don't know anyone that's had this happen to them, most people I know drive 32 through 30mph cameras, due to this, as I remember before I could even drive I said "what are you doing" and they said it's fine there' a leeway.

I have accidentally done it once and yeah no flash, but I wouldn't ever do it on purpose cause I have terrible luck hahaha.

Also I know people with a Dragy device, and again that always tells the truth that the speedo is under. As it seperates the bs from the truth when doing timed 0-60's/top end runs when cars have been tuned etc...

 

[Rroff]

Check it with your phones GPS and compare it to the local speed trap readout and your dial cluster.
I genuinely don't know anyone that's had this happen to them, most people I know drive 32 through 30mph cameras, due to this, as I remember before I could even drive I said "what are you doing" and they said it's fine there' a leeway.

I have accidentally done it once and yeah no flash, but I wouldn't ever do it on purpose cause I have terrible luck hahaha

Just Googled and there are calculators like https://tiresize.com/speedometer-calibration/ though they don't seem to quite match up with my experience. I think there is more to it than simply the circumference of the tyres. Depending on how your vehicle reads speed and maybe effect on the transmission, etc. I dunno.

 

[Removed User 345456]

Just Googled and there are calculators like https://tiresize.com/speedometer-calibration/ though they don't seem to quite match up with my experience. I think there is more to it than simply the circumference of the tyres. Depending on how your vehicle reads speed and maybe effect on the transmission, etc. I dunno.

Yeah tbh those things are what made me do my own testing, as I'd always been told by mates/people in the trade it was always in your favour, then found out myself this was true.

Even when I've ran really heavy wider bigger wheels, it's never made a difference, even with meaty tyres or when I've done the 'euro' thing and ran stretched too small tyres in order to clear a slammed flared arch car. So it definitely relies on the rolling mass being lighter to read slower and screw you over IMHO. As obviously less rotational mass = wheels spin free'er/faster, and the cars then lighter too etc etc.

FWIW regarding gearing, I always change my diff ratio in anything RWD and often my gearbox, with my E36 M3 box/LSD, I did this, along with way bigger wider wheels and massive tyres compared to stock, I had multiple sets of wheels, some staggered, some square setup, and yep no matter what I did, made no difference and never has screwed me over on the 5 E36's I've had, nor the civics/accord/nissan etc etc etc... Same goes for any of my mates cars.

Be it ABS reading off the knuckle/hub, or via the VSS off my LSD, it's never made a difference, regardless of the car - I always bin ABS on a RWD, so wire the VSS from the LSD direct to the ECU via the 2nd pin on the dial cluster, so it doesn't have a VMAX/limp mode issue, or completely reprogramme the VSS to the redline so no limp.

 

[Jonnycoupe]

Just Googled and there are calculators like https://tiresize.com/speedometer-calibration/ though they don't seem to quite match up with my experience. I think there is more to it than simply the circumference of the tyres. Depending on how your vehicle reads speed and maybe effect on the transmission, etc. I dunno.

Tyres squish too so the Static Loaded Radius is a lot different to what those numbers on the side wall suggest.

 

[Janesy B]

 

[Will Gill]

I'm in the process of replacing my passenger doors on my a4 after a boo boo I made months ago, quite proud of myself thus far, I've swapped both doors round all on my tod, it needs aligning but it started raining so now I'm back indoors trying to figure out how the hell to get the wing mirror off!








And yeah I did improvise and use an LSU as a door stand, perks of the job I guess

 

[Will Gill]

Wingmirror done, what an absolute delight it was.....I'd liken it to inserting a cactus us ones bottom, I'm sure someone somewhere loves it, not me!!!

 

[Diagro]

Wingmirror done, what an absolute delight it was.....I'd liken it to inserting a cactus us ones bottom, I'm sure someone somewhere loves it, not me!!!

Paint match is poor

 

[adam cool dude]

I did a similar thing when we first got our house about 15 years ago. Reversed the car out of the garage with the door open and bent it on the wall as I went out!

 

[Will Gill]

Paint match is poor

I'll get it cleaned at some point should make a decent difference, I'm over the moon, it was so embarrassing driving round like it was!

 

[Akagi]

Hopefully a clean and polish will help the paint match, because it's kinda unfortunate that it's a slightly different shade.

Definitely a vast improvement though!

 

[Axeboy]

Ordered a new van month's ago, was told system says March but didn't believe it. Bonus, it arrived at the dealer yesterday, I did not expect that.

Hopefully collect it on Friday.

Bad news though, I ordered a Ariel Nomad 2 or 3 years ago, checked yesterday and it's going to be next year at the earliest

 

[Will Gill]

Hopefully a clean and polish will help the paint match, because it's kinda unfortunate that it's a slightly different shade.

Definitely a vast improvement though!

I gave it £1 jet wash, what do you guys think now? (oh and I had a go at fixing the alignment too, that was fun