307 replies to this topic

[TFD]

Ok, will drop the front some more tonight. Aiming for the 130/140 allthough I allready have 10mm rake due tire heights. Front is 3mm lower than rear.

[stu8v]

Helpers don't fit with std springs. You would have to possibly go shorter due to clearance issues.

[thejoaoserra]

[quote][name="TFD" post="1839420" timestamp="1453467863"]
My vx is 148mm all around when complete OEM. Fitted the nitrons and after adjustment this morning front is now 141mm with just 2 turns from lose spring.
Maybe it will drop till 140mm tomorrow after bedding in over night but cant see this drop down to (148- 20mm) 128mm...[/quote] 
I'll ask nitron if a 1 in longer spring would allow us to set the car to OEM ride height (140mm) without putting to much preload on the spring to avoid damaging the damper.[/quote]
My understanding is this..

A longer spring will just change the point at which the collar sits on the shock body. For a given preloaded amount and (linear) spring rate the ride height will be the same. To reduce ride height you need to reduce spring rate or preload. As you can't reduce preload you need to reduce the spring rate. This is why you need helper/tender springs to achieve a lower ride height rather than different length springs.

Longer spring would allow a higher ride height as you can increase preload more before running out of adjustment on the shock body but I'm not sure this is what you're trying to achieve?[/quote]

I'm just trying to solve the problem when the spring becomes loose when removing pre load (adding negative pre load). Am i wrong to think it happens because the spring is to short?

What's the purpose of an helper spring in the case of solving the loose spring problem? Isn't it to occupy the space between the main spring base and the height adjusting collar?

Edited by thejoaoserra, 24 January 2016 - 10:57 PM.

[thejoaoserra]

I wouldnt panic about the fronts being loose too much. Main issue is keeping the rears in contacts. Fronts being loose doesn't worry too much.   With 17/17" wheel combo, 130/140mm ride height might be the lowest you want to go to keep the geometry at best. With 16" front wheel you loose some more height.

What differs so much with different tyre sizes? I thought the OEM sizes were close enough to the 16/17... If someone uses a 205/45/17" tyre in the front and 235/40/17" in the rear, will it make any difference to the ride height that gives the best geometry? Also, I've sent you a pm.

[Matthew Bentley Racing Ltd]

Well if you go from a 17" front wheel to a 16" (taking into consideration that the sidewall is taller on a 195/50/16 than 205/45/17) you still loose easy 15mm of ride height, so the spring platform would then we touching the spring and you would have 130f 140mm rear ride height.

 

Matt

[TFD]

How can a tire/wheel diameter effect geo-rideheight?

My smaller 215/40/17 tire will drop the front of the car by 10mm, so yes, it will be lower (but the tire/car gap remains). Will it affect the geo-rideheight? No. Geo-wise there is nothing changed when fitting smaller tires since there is no change in the arms.

 

When you change rideheight bij lowering the shock, yes, you alter the geo.

 

I calculate my rideheight geo-wise first, then with the tire/wheel combo.

 

My car all OEM setup was 148mm on all corners. Now geo-altering wise with the NSS it is 138mm front (1mm lose spring, can live with that) and 143mm rear. Thats a 5mm rake and as much as the front can take (for me, I dont like the idea of loose springs).

 

Now with my 215/40/17 and 235/40/17 tire combo I drop the front by another 10mm and the rear by 7mm. Final total rideheight is 128f/136r.

 

Grtz,

 

 

 

[Matthew Bentley Racing Ltd]

What was meant was this:

 

If someone was on 17" wheels all round and aiming for a ride height of for instance 130mm front and 140mm rear so they get a nice rake (for geometry), lowering the car by winding the spring platforms up to achieve this may result in a negative effect on geometry (wishbone angles for roll centre and bump steer being the main two).

 

In that senario you need to keep the wishbone angles as they are and don't want to affect the bump steer, the other option is putting 16" front wheels on. That will lower the front ride height, give you the rake needed and won't affect the wishbone angles or bump steer (probably why Lotus told Vauxhall to do it on the VXR).

[TFD]

[thejoaoserra]

Thanks!

 

I think I'm starting to understand this, the difference in the tire diameter is what determines ride height.

On OEM tire sizes: 175/55/17" (624mm)  and 225/45/17" (634mm) we have OEM ride height at 140mm front and rear.
with 195/50/16" (602mm) it lowers the car by 22mm on the front taking it to the 120mm ride height without changing the wishbone angles.

If I use 205/45/17" (616mm) and 235/40/17" (620mm) it will lower the car 8 mm on the front and 14mm at the rear... I guess with these tyres I could aim to 130/140, or can I go a little lower like 125/135?


[font="arial, helvetica, sans-serif;"]Regarding the loose fron[/font]t springs nitro[font="arial, helvetica, sans-serif;"]n says: [color=#2f4f4f;]There is only enough room for another inch on the springs on the street series.


PS: I'm using this [/color][/font]http://www.rimsntires.com/specspro.jsp to get the tire diameters. 

Edited by thejoaoserra, 26 January 2016 - 02:28 PM.

[siztenboots]

I found that the ideal spring length for a desired ride height or corner weight never quite met with a 1" multiple of length , so a 6.5" front spring with the right preload / droop , which is why I ended up having 2" helper springs on all four corners and shorter lighter main springs.

 

[TFD]

Thanks!

 

I think I'm starting to understand this, the difference in the tire diameter is what determines ride height.

On OEM tire sizes: 175/55/17" (624mm)  and 225/45/17" (634mm) we have OEM ride height at 140mm front and rear.
with 195/50/16" (602mm) it lowers the car by 22mm on the front taking it to the 120mm ride height without changing the wishbone angles.

If I use 205/45/17" (616mm) and 235/40/17" (620mm) it will lower the car 8 mm on the front and 14mm at the rear... I guess with these tyres I could aim to 130/140, or can I go a little lower like 125/135?


[font="arial, helvetica, sans-serif;"]Regarding the loose fron[/font]t springs nitro[font="arial, helvetica, sans-serif;"]n says: [color=#2f4f4f;]There is only enough room for another inch on the springs on the street series.


PS: I'm using this [/color][/font]http://www.rimsntires.com/specspro.jsp to get the tire diameters. 

 

An 8mm difference in tyre height means a (8/2) 4mm drop in rideheight. 14mm difference is 7mm drop  ;-)

 

grtz 

[Matthew Bentley Racing Ltd]

Why are you worried about the front springs coming loose?

[Captain Vimes]

Why are you worried about the front springs coming loose?

That. Also note that a smaller wheel/tyre will reduce ride height but it will increase the gap between the wheel and arch so if you're making the change for looks it may not achieve what you want. For performance and optimal geo it's a good move.

[thejoaoserra]

The idea of a loose spring doesn't sound very well... I'd like to avoid a bigger gap but if that gives better handling I'm OK with it, as that's what I'm after.

Edited by thejoaoserra, 29 January 2016 - 11:11 PM.

[Haston]

Loose springs when its jacked up won't cause any damage. I've corner weighted loads of race cars (Fiesta's and MX5's) and never had any problem. If it's a great problem or if for any reason you expect full droop that's when helper springs are required. I'm going to set it up to where it's pretty low and corner weight it and if the springs are loose it won't matter. You've not changed the rate of the spring or the damper just the position.

[TFD]

Anyway... did a short testdrive with the NSS and 1"arb fitted. Car feels more in contact with the tarmac and is way less crashy than OEM. Real test when the car is back on the road but feels allready good.

[Chrisspantin]

I dont suppose this group buy is going to be run again is it?

[thejoaoserra]

Don't think so, nitron is out of stock until at least July for the street series. Even I haven't got my set of dampers... Go for quantum if you can spend some more money.

[Lou_m]

How is everyone getting on with these shocks?

[GaryK]

They fitted nicely, and the car rolled out of the garage just fine when I pushed it. I then rolled it back and shut the garage