GolfGTIforum.co.uk
Model specific boards => Golf mk7 => Topic started by: Pretzel on 12 March 2020, 21:56
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Is it acceptable to change from 19" to 18" wheels on a car fitted with dynamic chassis control?
VW dealership suggests it shouldn't be done, I don't see why not if the tyre aspect ratio is increased.
Your thoughts appreciated
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Oh dear god.
NO, the wheels will turn square and you'll die!!!
Sorry, my mistake, it will be absolutely fine.
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Oh dear god.
NO, the wheels will turn square and you'll die!!!
Sorry, my mistake, it will be absolutely fine.
:grin:
The dealerships always know best... :whistle:
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Oh dear god.
NO, the wheels will turn square and you'll die!!!
Sorry, my mistake, it will be absolutely fine.
LOL, what he said... :grin:
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Hmmmm, I wouldn't go back to that dealership in future.
There will be no issues swapping from 19's to 18's.
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I can confirm this because I did exactly this...
My 19" Santiago's were too harsh on local roads so swapped them for 18" and shod them in some decent F1's in 225/40/18 (got rid of the 'orrible Bridgestones with the 19's). I used VCDS to change the tyre circumference to the same as what 18" wheels would be coded to (copied from Votex):
17 - Instrument
byte 3
bits 0-2
"tire circumference"
225/45-18 = 25.972" Version 6
205/55-17 = 25.877" Version 7
225/40-18 = 25.1" Version 3
I can confirm that my wheels remain round and have not gone not square :grin:, no issues with DCC or anything else and the ride is now much more supple in 'Normal' mode, previously I left it in 'Comfort' as it was just too jarring to use any other setting.
Imteyaz.
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Is the coding needed for accurate speed display? Its not needed for DCC is it?
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Nothing needs to be coded.
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I'm looking to go the other way and put 19"s on a car that comes with 18"s, afaik I've not got DCC (it's a paid extra option right?), I assume I'll have no issues at all with anything on board the car re speed display etc. I know the wheels will fit as you can get them as a paid extra option (have 19" Brescia's going on).
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There’s no problem, it’s a very common change a lot of owners make. Just look at www.willtheyfit.com and put in the sizes. If going for 19’s then you just go to a 35 profile and it keeps the circumference almost the same. My speedo is out by less than 0.2 mph for every 30mph, so it’s negligible at legal speeds
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They have to be flexible to allow for mandatory winter wheel/tyre rules.
The coding is interesting though, presumably that sets the car for the combo it was supplied with and is only for the speedo. It can't be for the adaptation of the DCC, as that'd be more interested in unsprung weight.
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There’s no problem, it’s a very common change a lot of owners make. Just look at www.willtheyfit.com and put in the sizes. If going for 19’s then you just go to a 35 profile and it keeps the circumference almost the same. My speedo is out by less than 0.2 mph for every 30mph, so it’s negligible at legal speeds
Cheers, thought that was ok and they were the size profile I was going for anyway based on what the wheels usually come with when ordered directly via VW.
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Is the coding needed for accurate speed display? Its not needed for DCC is it?
Nothing needed for DCC, the coding is only to correct the speedo reading I imagine (although it's inherently over-reading anyway). I didn't code the 18's for almost a year and it all worked fine.
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The coding isn't even needed! Do you think you get different coding on a car that comes from the factory with 19s on as an option rather than standard 18s? The answer is no so what's been done is absolutely pointless.
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The coding isn't even needed! Do you think you get different coding on a car that comes from the factory with 19s on as an option rather than standard 18s? The answer is no so what's been done is absolutely pointless.
And to develop this a stage further, if coding was needed, presumably it would need to be done periodically throughout the life of the tyres as they wear down. Tyres that are getting towards the end of their life would have smaller rolling radius (and circumference) compared to new tyres; maybe as much as 6-7mm difference depending on how worn the old tyres are, which would have a small impact on speedo reading. Is coding done to compensate for this? No, I don’t think so......
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The easiest way to prove this would be to get a sample of DCC cars that had different factory fit options and see if they differ. You can't just dismiss it without first looking.
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The easiest way to prove this would be to get a sample of DCC cars that had different factory fit options and see if they differ. You can't just dismiss it without first looking.
why would you even do that? The rolling circumference of the 18 and 19 VW wheels is near enough the same and not enough to cause the speedo to be out. Coding something that doesn't need coding is just pointless.
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I'm not suggesting you would bother, I wouldn't.
However, there's various settings you can code, they're there for a reason. If you're going to make a sweeping statement such as "Do you think you get different coding on a car that comes from the factory with 19s on as an option rather than standard 18s? The answer is no..." then I simply suggested a way you can actually prove your theory.
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Doesn't even warrant proving to be honest. This is probably the first post in the history of the mk7 golf that has even raised the question :grin:
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It is curious as to why the setting is in there.
I'll bet that any car leaving the factory has it accurately set for the wheel size.
Why is almost certainly for speedo accuracy... you know... Germans...
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Speedos are allowed a % to over read so the difference between 18s and 19s will fall between that %.
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This thread was over and done with at jv’s post.
Nail on head.
It doesn’t surprise me the VW dealership recommended not to change wheels, there can be many aspects to that ranging from ignorance to duty of care in case an owner rushes out to bolt on a set of pig iron lumpen things that cause undue stress on the suspension. A dealer will always recommend (officially) to leave everything well alone.
One thing I’m curious about with the OBD adaptations is whether they might adjust the steering to take into account wider wheels and tyres.
The R is notorious for having a rubbish turning circle when specced with 19’s from the factory.
My ED40 (manual) originally came with 18” wheels and had quite sharp steering and a decent turning circle. My TCR originally specced with 19” wheels definitely seems to have a worse turning circle often needing an extra shunt to get it into a parking space neatly.
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This thread was over and done with at jv’s post.
Nail on head.
It doesn’t surprise me the VW dealership recommended not to change wheels, there can be many aspects to that ranging from ignorance to duty of care in case an owner rushes out to bolt on a set of pig iron lumpen things that cause undue stress on the suspension. A dealer will always recommend (officially) to leave everything well alone.
One thing I’m curious about with the OBD adaptations is whether they might adjust the steering to take into account wider wheels and tyres.
The R is notorious for having a rubbish turning circle when specced with 19’s from the factory.
My ED40 (manual) originally came with 18” wheels and had quite sharp steering and a decent turning circle. My TCR originally specced with 19” wheels definitely seems to have a worse turning circle often needing an extra shunt to get it into a parking space neatly.
I thought all R's were blessed with a poor turning circle?
I changed from 18s (225/40) to 19s (235/35) and there was no need to change the amount the wheels turned. No rubbing on lock at all - admittedly the different offset may have been a factor in this but there was plenty of clearance around the tyre.
As an aside (and assuming the multiple GPS apps/tomtom are all accurate) it actually made my speedo more accurate (although it was a minimal change).
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I thought all R's were blessed with a poor turning circle?
I have a vague memory of owners complaining the ones with 19’s were even worse than ones specced with 18’s. Possibly a placebo effect(?)
My R definitely had a worse turning circle than the GTI PP I had immediately beforehand, both came originally with 18’s. I swapped to 19” wheels on both cars (all with different offsets but all 8J width) and never had any issues with fouling either.
I can’t directly compare R to TCR as it’s now over three years since i last sat in the driving seat of an R.
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My TCR originally specced with 19” wheels definitely seems to have a worse turning circle often needing an extra shunt to get it into a parking space neatly.
I thought this but kept putting it off as being my imagination! When I drive into a parking space I often have to reposition myself which I never did with the PP. Could VW have fitted the TCR with the R steering rack?
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My Mk7 R with 19” factory wheels had an appalling steering lock. my Mk7.5 GTi PP with 19” factory wheels is night and day better :shocked:
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Just a thought, but even tho' rear drive shouldn't be engaged, do they have less steering lock to limit the speed difference between the left and right rear wheels when maneuvering, which would ordinarily cause diff wind up in a permanent 4WD vehicle?
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Even though the Haldex uses clutches to engage and disengage drive (rather than permanently coupled 4WD) the reduced steering lock must still be at least in large part to do with the diff. I’m sure there are a good few R owners on here who must know the official reason(?).
God knows why the TCR seems to have a poorer lock than a regular GTI though.
Anyway back on topic, as said here many times, it’s fine and dandy to change up a size of alloy wheel even with DCC but do try and get a fairly lightweight wheel (or at least a reasonably comparable weight to the wheel coming off) and keep your tyres correctly inflated to reduce any additional wear as much as possible. The car will drive better with lighter wheels and proper air pressures and it won’t wreck ride quality. .