Springs for a 1.4i vs 1.4tdi

[Robin_Cox]

A few weeks ago I refurbed the front end of my 1.4tdi SE (with aircon, without OSS, non Sport, 16" wheels). From discussion here I was guided towards Monroe SP3248 springs with Bilstein B4 shocks at the front. Ride height same as before ; ride is firm but spot on. Weight range / spring : L50 / 8Z0 411 105 AL - 3 blue one silver.

I'm accumulating parts to refurb the front end of my significant other's 1.4i SE (same spec but petrol engine - 16" wheels), which I understand is considerably lighter at the front end than the Tdi. I have B4s again as the shocks are worn, and may as well do the springs (+strut bearings, drop links, ARB bolts etc.). 7zap cross referred with the option code list refer me to weight range / spring : L23 / 6Q0 411 105 AM, yet a hunt for equivalents comes up again with the Monroe SP3248 as well as some unknown-brand alternatives on Ebay etc. Looking under the car, the springs look lighter gauge and have several more turns visible than the ones on my Tdi so I assume are softer-rated than the Tdi ones. If I put the same springs as my Tdi on I suspect that it will either ride very high or just be wrong due to the lack of weight. Is this a misunderstanding, or does anyone have any suggestions of aftermarket springs that will do the job for a 1.4i (standard height & normal ride)?
Many thanks for any comments.

 

[bono05]

Hey. I put myself a rack for 1.4 gasoline with 1.4 TDI (in front), the ground clearance is increased by 10 mm max. Skating on bad roads is very good!

 

[Robin_Cox]

Today I....

picked up the above 1.4i (non-OSS) car following the front end rebuild. Amazing transformation - less firm than my 1.4Tdi but still extremely smooth on our less than perfect roads, and I'm really impressed. A month ago after my original post, to try to get the info I wanted I went through the various online suppliers and compiled a spreadsheet of the majority of A2-specific springs from various suppliers for whom basic information such as the spring-wire thickness, spring diameter, and height are supplied.

From this an approximate table of relative spring rate using the spring rate equation could be compiled to compare various options. In some cases, where available, model-specific information included by the suppliers was included, although this seems to be a bit random. Additionally, there are some conflicts on data (ie, overall height) for the same model of spring from different sources, but there are enough examples for which data can be correlated from a number of sources that suggest one can identify springs with similar rate but (for instance) 25mm difference in height that could be used for lowering or raising a car without dramatic impact on ride quality. This doesn't include several springs for which information isn't given (for instance, the Monroe SP3248 on my Tdi doesn't have data I can find online, but they're at the firm end of the spectrum based on my own measurements and what I can feel). I attach this table as a PDF, followed by a larger PDF list tabulating rates and heights of springs for various A2, Polo, Skoda and Seat models of roughly similar dimensions in case any of these are of interest for comparision.

Based on this, I decided to try the Suplex 3207 at the soft end of the scale with standard height, paired with Bilstein B4s - and based on an extremely unscientific 7 mile drive home this combo is bloody brilliant. Not sporty, but for everyday use nigh on perfect.

POSTSCRIPT (4 years later). The Suplex 3207s were good .. until one snapped without warning on low miles less than 7 months later - and this seems to tie in with other reports of questionable quality in Suplex / Spidans in recent years. I replaced them with the Sachs springs in the table nearest in spring rate which had much the same characteristics but remain unbroken over 3 years later.

 

[Vorsprung durch Technik]

Good work finding all this information, i take it the info on the far right is for poundage rates? Just to add Supplex springs used to supply Jaguar back in the nineties and possibly beyond or still do. Based on that i bought a set for my Sierra 2.0i ghia back then.

Do you have a link for the supplex springs and cost? This combination you mention sounds superb! What B4 shock did you use? Gas or oil? Cheers Mark.

 

[Robin_Cox]

I used the equation featured for compression springs on the following website pasted below. Just to confirm - these numbers are not absolute poundage rates, but approximate relative spring rates based on supplied data for the springs. Obviously it depends on the information being supplied accurately, but there are enough that are probably close enough that the bulk of the table can be worked with to give you an idea of where a spring option lies in the range of those available both on spring rate and overall height (assuming data I've used is correct). After that point, there is a bit of "suck it and see / caveat emptor". Or just ask what other folk have used!

https://www.engineersedge.com/spring_comp_calc_k.htm

k=Gd^4 / (8nD^3)

d is the spring wire thickness ; D is the coil diameter, both translated into inches. See the page above for the rest of the parameter definitions.

The B4s were Bilstein B4s - 2x B4 Front Kit Gas Pressure Car Shock Absorbers Dampers 22-105813 from TDC automotive (Ebay shop), £63.88 including VAT (varies up and down by a couple of quid - my car's ones were 66 quid)

The springs were :

https://www.ebay.co.uk/itm/Suplex-C...376602&hash=item51f475d871:g:2k4AAOSwTM5YtZ36 - 22-23 quid each from Discount Car Products in Northern Ireland (slight variation over time), took a good week to deliver but spot on service, replied fine when I asked questions through Ebay etc.

Also put in Meyle top strut bearings & mount, economy drop links (ended up being Stark brand), Febi ARB 16mm bushes & retaining strap and bolts, new pinch bolts as part of the build all supplied by Autodoc or other Ebay suppliers.

 

[Vorsprung durch Technik]

Thanks again, mine are B4 gas too which is reassuring. I'm a great fan in genuine Audi springs just not their silly prices, believing their huge r&d department get it right but there's always that nagging doubt that even Audi may have missed a trick.

Incidentally what was the 1.4 petrol non (oss) like to drive before these changes?

These Supplex springs sound very interesting because i've never heard them mentioned within these pages however i know their pedigree. It would be nice to know if your 1.4 was an se version and whether you decided to buy these Supplex springs because A, you thought they were softer than se springs going by that chart or B, would be the same rate as an se or even C a slightly higher rate? Whatever has happened because of this choice of setup it's intriguing going by your description and i'm absolutely sure a Member who joined last year from memory "Merlin" who complained bitterly about the ride would also be very interested! ?

Cheers Mark.

 

[Robin_Cox]

Hi Mark,

yes, it was a 1.4i SE (52 plate) complete with aircon, without OSS on 177,000-odd miles when I picked it up from Glenrothes a month ago. The car is on 16" SE rims with 195/50/16 tyres. £350 on Gumtree. The test drive highlighted serious braking and suspension deficiencies in that the car rode like my old 2CV and braking needed one to plan ahead (front discs were very badly corroded and the pads were among the worst the mechanic had seen for years, only one drum had any braking effect and no apparent handbrake), but it had a valid 6 month MOT and I figured for the money that I could get the brakes / suspension / other jobs done that one does with any A2 of this age and then it should be good to go. Also helped that cosmetically it just needed an interior valet but generally it was pretty smart in appearance for a car at that price.

How it rode before was compromised by knackered ARB bushes or drop links making loud knocking noises on potholes, the front left shock being empty and the rear shocks also having no apparent damping effect - so it drove pretty crap being honest! It seemed a bit crashy but difficult to tell otherwise. At the time of asking above for front spring recommendations, I checked the 7zap parts list to identify the P/N recommended for the car going by the options list sticker in the boot. This identified an Audi (~VW Polo) model number of spring that didn't have a direct equivalent supplied by any of the after-market suppliers. As it was nowhere near as beefy as the spring on my 1.4tdi I guessed that it would be an idea to work out approximate coefficients for all similar aftermarket springs I could find info for that also had a 6Q or 8Z reference because several websites suggested using the same spring as my Tdi (which seemed daft), and then I decided to just go for one at the soft end of the spectrum in the end on the basis that my partner wanted comfort rather than a hard ride on our roads.

In short then I can't actually say I chose the springs on the basis of knowing where on that table the original springs would feature, but my guess is that they would be somewhere in the middle with a calculated rate of ~"155-160". The 3207s are "150" so a fraction softer, but with B4s perhaps slightly firmer damping than some options. Having now experienced the ride on the road instead of on paper I am happy, but I guess with some combinations of options that other people might want or need something different - and I hope the lists are of some use in guiding this decision.

 

[Vorsprung durch Technik]

Thanks for the info Robin much appreciated. Knowing that you went for a slightly softer spring would explain the excellent ride given our poor roads and all new makes a huge difference to a car that was hanging as you described. Very pleased for you and sounds like an inspired choice!

Cheers Mark.

 

[steve_c]

Robin, thanks for your careful research on this. Do you have any thoughts on what would be the best springs for the rear suspension to match the Suprex 3207 at the front?

 

[Robin_Cox]

At the moment I don't, but I should probably perform the same kind of analysis starting with 7zap and the list of possible part numbers to determine another ranking list similar to the above. Luckily the back springs on both of our cars were in considerably better nick so I didn't need to order these, but it would be useful for the future. The only problem is that I have no means of testing these ones when I get round to it so it would be an indicative resource only.

What came to mind after I'd driven my Tdi into work over the same roads this morning was the following. The spring / shock choice above on our 1.4i has given it a front-end ride that is reminiscent of a typical mid-range (i.e. non-sporty) French hatch such as a 90s Clio before they started aping Germanic ride characteristics - i.e. accommodating of poor surfaces and secure without being 2CV-floaty, but definitely not as firm as my own car (which being a Tdi would probably wallow a bit with the same springs due to the greater weight over the front wheels). Mine isn't harsh, but it isn't as compliant as the above.

 

[Robin_Cox]

Using the same idea, I've collated most of the A2 aftermarket rear springs I've been able to get numbers for without a big hunt - please see attached PDF - these range from springs for 1.2, then cars without OSS, then cars with OSS, and then some that are perhaps Sport grade (higher rate with lower overall height). These have been correlated with the nearest equivalent 8Z model when this has been suggested. Again, a relative coefficient of spring rate is calculated, then the table was sorted into groups based on this. There may well be more springs within the VAG group that can be used for extra lowering / higher or lower rates for specific applications that could also be usable but I haven't yet done a broader search.

 

[Robin_Cox]

Robin, thanks for your careful research on this. Do you have any thoughts on what would be the best springs for the rear suspension to match the Suprex 3207 at the front?

Going back to your specific question, Steve, both the Suplex 03172 and the Spidan 49546 seem to have identical scores at the soft end of non-OSS 1.4l range, so if I was looking I'd probably go for the 3172s to match the fronts, along with the Bilstein B4 shocks I have already fitted. Since Suplex also seem to be easier to get hold of than Spidans in the UK that would also tip the balance for me. I remember seeing a thread here where someone (Timmus?) has paired Spidan 49527 (front) and 49546 (rear). This would be about 10% higher rate at the front than the 3207s, but should be identical at the rear - but bearing in mind I think he has a Tdi the stronger front-end would be necessary.

 

[steve_c]

Robin, thanks again for putting yourself to so much bother, it's much appreciated.

Going back to the front springs, it seems strange that Suplex designate their 03207 as being for A2s with OSS and 03171 for A2s without, where your calculations suggest (to my inexpert eyes) that they belong the other way round.

 

[Robin_Cox]

some of the designations online seem a bit random, to be honest - the ones I trust most are the manufacturers' own information, but unfortunately most of the info is on discount parts warehouse sites. I've also found two sets of numbers for 3171 - the second suggests that they're 330mm high with a diameter of 138mm, which would make them half an inch lower and slightly stiffer. I think in the end it is possible to get too fixated on precise numbers and designations, especially as the data sources are open to a degree of question.