low profile tyres

citrov6 · Post by **citrov6** » 08 Feb 2010, 19:40

This was more of an experiment, since I wanted to change the alloys, also 15" because the ones on there feel a little clumsy for track days that I did in summer. So I found a set but they were 7" wide opposed to the 6 or 6.5" factory ones, on which 205mm tyres popped of so I needed something wider. looking through the list the closest options were +/-5% out from the factory tyres 225/50r15 low profile which are the only ones I've tried so far, and 215/60r15 high profile.

I noticed the ride became firmer ofcourse, but I also noticed the resonance for this xantia is at 60-70mph. I think if it switches to hard mode it becomes more pronounced although that is a complicated issue of frequencies from the damping ratio that I have not done for a while. Next tyre change I will try the 215/60r15, they will give about an inch more wall, but mostly they will give a change in spring of the side wall load capacity will be 94, with the current they are 91, values at max inflation.

If not for the resonance the car drives very well on these tyres not excessively hard, but definently responsive, not activa like but reasuringly stable on roundabouts compared to before.

Napolian · Post by **Napolian** » 10 Feb 2010, 10:32

I fail to understand what you are trying to achieve with low profile tyres. Low profile tyres are not ideally suited for general road use at the best of times never mind the appalling state of British roads and fitted to a car not made for that specification. Furthermore, if God forbid you have and accident, I have no doubt the insurance company would say that your insurance is invalid.

Deanxm · Post by **Deanxm** » 10 Feb 2010, 17:40

Told the insurance about my wheels, didnt really add much to the premium if im honest, im running 215 45 R17 as offered as an option on the XM MK1 and the feel and handling is much improved, braking is also very much improved to a noticable degree.
I have no problems with the lower profile tyres and if i had to ovoid an elk.............on the isle of wight................i know what shoes i would want the car wearing to do the job.
As far a resonance is concerned i found drilling the centre hole in the strut sphere damper to 1mm counteracted that quite well, although when i do the engine swap i will go back to standard strut spheres to preserve sports mode and drill out the hydractive Dampers instead.

I fail to understand what you are trying to achieve with low profile tyres

I would imagine since V6 does track days the lower profile tyres on standard rims will alter the final drive ratio giving better accelleration and the lower profile of the tire will offer better support to the sidewall meaning the tyres are not so willing to scrub the shoulders off when pushing on a bit, of course being wider they will give better dry weather grip with like for like tyres and improved handling responsiveness.

D

citrov6 · Post by **citrov6** » 10 Feb 2010, 18:26

Interesting, I was thinking of putting XM 0.7 spheres on like I had read on a previous thread for their slightly higher damping though that is an interesting idea. This was the link http://www.lozian.co.uk/sphere_table.pdf (link now working originally from here http://www.gsfcarparts.com/forum/viewtopic.php?p=15131). But I think soft mode bumps up damping by +1.0 anyway (not sure if that is right) so that may not help much.

Yes those were the reason for changing them thanks for explaining, and they did the job very well. However it will be used for the road mostly now and I would like to keep the wheels they do feel more reasuring to me.

Post by **Peter.N.** » 10 Feb 2010, 19:13

It does seem rather counter productive, you buy a Xantia presumably for its soft ride and then set about spoiling it by fitting low profile tyres.

citrov6 · Post by **citrov6** » 10 Feb 2010, 21:06

Haha, yes, thats why we have 2, the red one is as the factory put it together still rides like it used to, we've been driving it for sometime like that, but since getting the second one, something in me can't resist enjoying trackdays unfortunately, maybe with a few more grey hairs I will.

Also the xantia is probably the best compromise with a normal car and a citroen with its anti sink and hydractive, its not completely squishy, if I was travelling one end of the country to the other a CX or BX would of been what I'd want, but as it is I want a touch of the squishy ride but be able to go from site to site easily and agility in the town centre when I get there is something that makes rush hour more negotiable for me.

Though I'm looking forward to going back to big tyres and the squishy ride, I'll look into that drilling mod sounds like what it needs

Stempy · Post by **Stempy** » 10 Feb 2010, 22:44

For track days you could always force it into permanent hard mode by removing the HA ECU fuse, then just plug it back in for the drive home.

Post by **Peter.N.** » 10 Feb 2010, 22:52

I should get a BMW instead

evilally · Post by **evilally** » 10 Feb 2010, 22:54

Have you considered a set of R888's?

Stempy · Post by **Stempy** » 10 Feb 2010, 23:00

Peter.N. wrote:I should get a BMW instead

I think I'd at least like manual gearbox for the track, an Activa would be the way to go.

Deanxm · Post by **Deanxm** » 10 Feb 2010, 23:10

I have to say the point is being missed somewhat here and i understand what V6 is doing, a BMW is like riding a cheesegrater down a mountain..........all the time, ok it has RWD for pure hooligan value but A hydractive Citroen can do both that is the point for me anyway, i know you can get them to ride like a jelly but if you get the tire /wheel/sphere options right you end up with a car that wafts nicely in general use but has precise steering with a good turn in and minimum body roll (for the comfort it gives) in one car, obviously it will never be an Activa or M3 on the track but you can set yourself up a very confident car none the less.

unplugging the hydractive ecu will make things worse in my mind, the idea is to stop the car rolling over on the shoulders of high profile soft tyres, stop this roll and you get pricise steering and evenly wearing tyres.
After all the ecu will give you hard mode when you need it, thats the key to the hydractives exellence.

Never tried Toyo's myself but i have heard very good things about them.

D

Post by **Peter.N.** » 10 Feb 2010, 23:29

Mmm, my ride is to hard for me working properly and with the correct tyres

citrov6 · Post by **citrov6** » 11 Feb 2010, 01:16

Deanxm has it exactly, the xantia gives not just an inbetween car but a car that has a foot in both worlds, its not an activa unfortunately nor does it have the agility and power of an m3 but I can make a 3 hour trackday, the 3 hour drive to get there and walk round the shops with the missus without clenching my back and needing to sit down. Same every day i don't feel tired i feel refreshed and not fatigued from back ache and not having any near misses on round abouts, all in all a fantastic car and hopefully will keep these running on the roads until the petrol stops being available

Stempy · Post by **Stempy** » 11 Feb 2010, 11:05

Deanxm wrote:
unplugging the hydractive ecu will make things worse in my mind, the idea is to stop the car rolling over on the shoulders of high profile soft tyres, stop this roll and you get pricise steering and evenly wearing tyres.
After all the ecu will give you hard mode when you need it, thats the key to the hydractives exellence.

D

All very true, but I don't think it was programmed with track days in mind

lexi · Post by **lexi** » 11 Feb 2010, 15:14

It`s low profiles on 4X4s that make me laugh