jammy Posted November 24, 2018 Report Share Posted November 24, 2018 So I am running 19" vectra vxr alloys on my 3.0 v6 cdti signum and I am running them at 40 psi front and rear.. I've seen supposedly official data stating 32psi front and 30 rear for a signum with oem 19s and then some supposedly official data stating 44psi front and 36 rear I'm lost at this now, The tags on my car don't list pressure for 19s as my model came with 17s as standard (19s were available as option extras and also some irmscher spec cars came with 19s standard so there must be correct numbers available? I first thought 40psi was to much but many seem to be running 40psi but I am wondering if 40psi is to much and a reason why I'm loosing grip Quote Link to comment Share on other sites More sharing options...
jammy Posted November 24, 2018 Author Report Share Posted November 24, 2018 Tyre size is 235/35/19 Quote Link to comment Share on other sites More sharing options...
Rich Posted November 24, 2018 Report Share Posted November 24, 2018 Could the higher rating be for when the car is loaded? Pressures are only a guide and I've always used what's the label with no issues, usually 32/33psi on 17s. Isn't the internal volume the same on the 19s as it is on 17s. How does the car handle on 40psi? Have you tried dropping it to see what happens? Quote Link to comment Share on other sites More sharing options...
jammy Posted November 24, 2018 Author Report Share Posted November 24, 2018 Up untill it's got colder seemes on but it's loosing grip quite easy now and I am wondering if the twitchy front is due to to much air? 32psi my 18s looked flat so they lived on 38psi.. I was brought up on the basis of take the wheel size and double it and then plus 2 and that's your psi.. Over the years it's sort of been true to form Quote Link to comment Share on other sites More sharing options...
Rich Posted November 24, 2018 Report Share Posted November 24, 2018 I've never done that, I run at 32/33 apart from the MX5 which is on 26psi for extra grip! What tyres are they, could it be the compound is going hard in the cold so you're losing grip? Quote Link to comment Share on other sites More sharing options...
jammy Posted November 24, 2018 Author Report Share Posted November 24, 2018 Mitchelin sport contact thingys... As its fweeeeeeezin cold here I've just been out and dropped to 36/34 which has made it a less crashy ride, and seems to of calmed down the twitching and tramlining somewhat.. Tbh I've never had 19s before and other than my old red mk3 astra years ago its only been the last 2 years I've ran 18s.. If the arches weren't so massive on cars these days I'd happily stick with smaller wheels tbf Quote Link to comment Share on other sites More sharing options...
SMARTLY Posted November 24, 2018 Report Share Posted November 24, 2018 Have you got a manual for it, if so look in there. Quote Link to comment Share on other sites More sharing options...
Rich Posted November 24, 2018 Report Share Posted November 24, 2018 Looks like it should 42 front and 38 rear with up to 4 people. Fully loaded is 45/51!!!! Quote Link to comment Share on other sites More sharing options...
jammy Posted November 24, 2018 Author Report Share Posted November 24, 2018 55 minutes ago, SMARTLY said: Have you got a manual for it, if so look in there. Yes but as my car didn't come with 19s It does not specify And omg 42/38 that will be harsh as f**k :0 Quote Link to comment Share on other sites More sharing options...
jammy Posted November 24, 2018 Author Report Share Posted November 24, 2018 I ran 40 to save my wheels from . Getting cracked.. I didn't think I was far fro. The truth tbh but that seems extravagant.. Most of the time it's just me and a few bits of crap in the boot.. Most that would be is 4 but very rare Quote Link to comment Share on other sites More sharing options...
Tony Posted November 25, 2018 Report Share Posted November 25, 2018 Rich is correct. Within reason, the pressure indicated are a suggestion. Go up you'll reduce the tyres contact patch ( less grip ) but also less roll on corners ( slip angle ) go under more grip but more slip angle. Quote Link to comment Share on other sites More sharing options...
jammy Posted November 25, 2018 Author Report Share Posted November 25, 2018 42 front seems a lot as even I think 40 is a bit much.. Were out and about today in the car 2 adults one child so I'll see how it behaves set at 36/34 Quote Link to comment Share on other sites More sharing options...
Rich Posted November 25, 2018 Report Share Posted November 25, 2018 I would never run pressures that high, I won't even go above 35. The BMW has 18s and the pressures on those are 32/33. If you're happy with 36/34 just keep an eye on the tyre wear. Quote Link to comment Share on other sites More sharing options...
Tony Posted November 25, 2018 Report Share Posted November 25, 2018 On the Lexus IS200/ 300 i re-wrote the front geometry on them and on testing every 1000 miles the only inherent trait was under inflation tyre wear so i changed this from 33psi to 35psi....( small amounts ) and that solved the problem. Quote Link to comment Share on other sites More sharing options...
jammy Posted November 25, 2018 Author Report Share Posted November 25, 2018 Yeah it's tyre wear that's going to bother me given the price to replace them.. Car doesn't seem to slip away from me now but a little wobbly on direction change threw bends so gpigg to up it to 38/36 which I think will be just right for me.. My honda only runs 34/34 Quote Link to comment Share on other sites More sharing options...
Rich Posted November 26, 2018 Report Share Posted November 26, 2018 18 hours ago, Tony said: On the Lexus IS200/ 300 i re-wrote the front geometry on them and on testing every 1000 miles the only inherent trait was under inflation tyre wear so i changed this from 33psi to 35psi....( small amounts ) and that solved the problem. It's amazing how such a small difference in pressure can have an impact on the tyre wear. Quote Link to comment Share on other sites More sharing options...
jammy Posted November 26, 2018 Author Report Share Posted November 26, 2018 I've settled at 38/36 More feel in the steering plus I can feel the tyres gripping front and rear now 36/34 actually felt like the tyres were under inflated.. Don't spin the front wheels as easy now too It's become a more pleasant ride too.... I'm 99% sure I've found my happy medium with the cars set up now. Quote Link to comment Share on other sites More sharing options...
SMARTLY Posted November 26, 2018 Report Share Posted November 26, 2018 Check the wear after 500 miles Quote Link to comment Share on other sites More sharing options...
jammy Posted November 26, 2018 Author Report Share Posted November 26, 2018 Aye mate I'm checking weekly any way as although I have my work car I still manage to wack up some milage on this of an eve and weekends.... At 40psi over 2500 miles I haven't noticed any wear issues front or rear.. Pretty sure the front will wear well with just 2psi less but the rear does concern me given its been lowered and running more camber than stock but everything is in the green and well within peramiters so I am hopefull Quote Link to comment Share on other sites More sharing options...
Rich Posted November 26, 2018 Report Share Posted November 26, 2018 Nice one, it's amazing the difference 2psi can make. Quote Link to comment Share on other sites More sharing options...
jammy Posted November 27, 2018 Author Report Share Posted November 27, 2018 Now I can start thinking about cosmetics want to get the car tidied up as I want to get me a 530d tourer within the next year Quote Link to comment Share on other sites More sharing options...
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