All Things Mk5 > Members Rides
Very budget track build
Clarkj93:
Front SP bushes turned up.
Got the new adjustable Combrake top mounts ready to fit with linear springs I need to order. Compbrake get a mix of reviews on quality but these top mounts do look and feel very nice, time will tell how robust they are.
So next step is to attach a linear spring, the Compbrake top mount will accept a 2 to 2.5 inch ID spring and the Bilstein spring perch is for 2.5 inch ID springs so it is simple enough to just stick a 2.5 inch ID spring in there, the springs are also just over 8 inches long. I tried calculating the spring rate of the progressive spring, its quite tricky to be 100% confident like you could be with a linear spring. Here is the method I used to figure it out:
This article was useful https://shocktherapyst.com/the-truth-about-dual-rate-springs/#:~:text=The%20formula%20for%20a%20dual,125%20lb%20combined%20spring%20rate. it made me realise that these "progressive" springs on the market and really just cheap to produce dual rate springs.
So after realising this I calculated the spring rates as Rate 1 and Rate 2. Rate 1 being the initial softer rate and Rate 2 being the stiffer remaining rate. I split them by the coils that had protective tubing on and the ones that did not, the reason for this is as the article explains that a dual rate spring like this will result in Rate 1 fully binding together and taken out of the equation ad then Rate 2 taking over so I thought it was semi-safe to assume that coils with the tubing are the ones that bind and therefor are part of Rate 1.
So this gave me the results for the front spring:
Rate 1 = 225 lb/inch - 4 kg/mm - 39 N/mm
Rate 2 = 343 lb/inch - 6 kg/mm - 60 N/mm
slightly different to the results I found on this thread a while back https://www.mk5golfgti.co.uk/forum/index.php?topic=31277.0
I'll paste it here:
B16 PSS 10 Golf 5:
215 f, 285 r (both progressive)
Front: E4-FD1-Y704A00 = progressive; initial rate 32.8N/mm (approx 190lbs/in), secondary rate 43.4N/mm (approx 250lbs/in)
Rear: E4-FD1-Y754A00 = progressive; initial rate 33.0N/mm (approx 190lbs/in), secondary rate 50.1N/mm (approx 285lbs/in)
At static height:
>> 39 and 51 N/mm (R32 B16: 250F and 285R lbs/inch)
So on that basis and my previous understanding that an additional spring rate of 2kg/mm OR 112 lb/inch OR 20 N/mm should be well within the ideal tolerances of the valving.
So I will most likely opt for Faulkner race spring of the following rate:
450 pounds/inch - 8 kg/mm - 79 N/mm
A little stiffer than my calculations OR a lot stiffer if I have ballsed the calculations up and the previous thread got it right :grin: but just going to linear I imagine will have the effect of feeling like a stiffer spring rate anyway as there is not any initial "give" like the dual rate stuff.
Scheero1312:
I though of a good idea for the intake on your track build.
Take out the bottom fog light have a tube or pipe running from where the fog light used to be and to a cold air intake.
Let me know if you try this and how it goes.
Clarkj93:
--- Quote from: Scheero1312 on March 13, 2023, 11:23:28 am ---I though of a good idea for the intake on your track build.
Take out the bottom fog light have a tube or pipe running from where the fog light used to be and to a cold air intake.
Let me know if you try this and how it goes.
--- End quote ---
1 step ahead of you :happy2: not sure how effective it is mind you, would be better if it was directed to a sealed up alloy air box I think
Clarkj93:
So a lot of trial and error, wrong springs, drilling, angle grinding and we have a finished setup. In the end I used the b14 damper, with 7 inch 450 pound springs at front, with a Compbrake 2.25 inch top hat and Compbrake adjustable top mount. Anything bigger than 7 inch is like OEM ride height at this stiffness I found.
Also cleaned up the TT arms and fitted with super pro bushes.
The mk5 consoles with TT solid bushes are now in a box after being cleaned up if anyone wants them
Love a suspension shot...
I still need to finish off 1 or 2 little jobs on front end, sort out some more efficient brake ducting and then onto the rear, found a local shop that is happy to sand blast and powder coat the subframe and control arms for 300 quid so may get that done in grey/silver so matches the front control arms and subframe and then fit with SP bushes all around. Will be a little while before I can do a real test drive on the road of how this setup behaves.
Also got my eyes on a Varley red top 25 battery too which is about 10-12kg further weight saving which I think I will mount behind where the passenger seat would be.
Clarkj93:
Very frustrating update - having paid for and tried multiple spring lengths along with helper springs I've concluded that its just not possible to use a linear spring with these dampers without causing other issues.
Due to the damper design maybe being too long that it gives the following issues:
- a 450 pound 7 inch spring requires a helper spring to get a good ride height, however this the spring perches are obviously not designed for this in mind as the helper perch and spring perch come into contact as you can see
- Also at the ideal ride height there is only half an inch of bump travel.... which is 1/8th of the dampers travel which is very detrimental and may even be un-driveable. Raising the car to half about 50% of total travel for bump which is the minimum you would want really makes the ride height so high it may as well be an off-roader build instead. You might be able to see from the pics how high it is, although in real life it looks way worse!
So yeah the resulting options are....
- use a very very soft linear spring, that will give a consistent feel, allow for more camber but be way too soft on the track
- use a stiffer linear spring, that will give a consistent feel, allow for more camber but have almost no bump travel
- use a stiffer linear spring, that will give a consistent feel, allow for more camber but very very high ride height and then high CoG
- continue to use bilstein springs, that are overly soft before being loaded up on turn-in and only allow the car to a max of -2.3 deg camber but allow for a ideal ride height and so a much lower CoG
So in my opinion the only option is to continue to run bilsteins, pretty crappy result after all the effort and money I've put into this.
This article sums up the fundamentals well here, although took me some time to really grasp some aspects and do some other research on top https://suspensionsecrets.co.uk/coilovers-installing-and-setting-ride-height-correctly/.
I know a lot more about suspension than I did a month ago but left feeling quite deflated after wasting quite a number of hours of taking the suspension on and off and wasting a good chunk of money over a spring and solid top mount collection....
So I think next I will refit the bilstein springs, sort out some better brake ducting and get the thing booked into retro resus then for a few jobs:
- rear control arms refurbished and bushings changed ( I took some of the arms off the other day, bushings are awful and I cannot be bothered with doing it myself now)
- ditch the aircon and majority of air bags
- corner weight
I was going to switch to a Varley red top battery and get it relocated towards the rear of the car with an internal cut off switch but think I may just look to save some cost for now and maybe stick in a basic toyota aygo battery or something for 40 quid off of ebay as a quick cheap solution for now that still saves 7+kg.
If anyone does want a brand new set of Compbrake top mounts, or even any length of 450/375 pound springs, let me know.
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