Subframe Brace MK4 GTI – Are they worth it?
Is it worth fitting a subframe brace to your car (especially if it’s a older model)? Are subframe braces worth the price and the hassle of fitting? Let’s find out what by seeing what happened when I installed a DIY front subframe brace to a VW MK4 GTI/Audi TT chassis, in this specific case a Octavia RS MK1.
Factory Subframe Reinforcement Solution
The Audi TT MK1 had extra chassis stiffening from the factory, over and above the other cars that used the same chassis eg Golf GTI MK4, Leon MK1, Octavia MK1 and Audi A3 8N. I assume because the TT was sold as a cabrio.
Part of this extra stiffening was on the front subframe which went between the front wishbones. The factory bar uses holes already present in the subframe. (Alas the factory part is now longer available)
I DIY’d my own brace copying the factory item by using a straight piece of aluminium box section and rivnuts.
I inserted the rivnuts into the factory subframe, measured the distance between the holes, cut the aluminium box section (2cm wide, 1cm high) to length, drilled holes in it and fastened it to the threaded rivnut holes in the subframe with a couple of bolts. Job done.
I also super glued some plates to where the bolt went through the aluminium box section to giving the holes some extra strength.
What Difference Did The Subframe Brace Make?
The difference was not night and day but I think there was a noticeable improvement.
Imagine sitting on a three legged stool where the legs are slightly loose where they attach to the seat.
Now imagine the legs are solidly mounted to the seat and the legs of the stool now give a slight shock absorber effect.
This is how I would describe the difference between no chassis brace and a chassis brace on this specific chassis.
The front of the car seems more tied together.
It feels less loose and the dampers seems to be doing more work.
Handling Difference
That’s the difference in the ride, how has the handling changed?
Not such a big difference in this respect.
Perhaps the car turns in more decisively. There may have been a very slight delay between turning the wheel and the car turning before. It seems more positive now, less delay.
There may also be a very slight uplift in the amount of grip. For sure not night and day but maybe slightly more.
Was The Subframe Brace Worth It?
On this car (Octavia MK1, VAG MK4 Golf platform) I would say 100% yes. Absolutely it has not made things worse. The ride of the car seems better, the car feels more solid and on top of that the handling might be very slightly better as well.
The bar for this car is extremely simple, a straight piece of bar with two holes in the end will do the job. There are aftermarket lower front bars that use the bolts that attach the front wishbones. I prefer the rivnut solution because unscrewing the wishbone bolts might cause you to have to get an alignment. I think this is unnecessary because there are holes in the subframe we can use.
All in I think the cost of this DIY bar is less than 20 Euro (if you already have the rivnuts and the rivnut installation tool). I think if it cost a hundred 100 Euro it would still be well worth it.
Parts Lists
If your interested this is the list of the parts I used. (Different cars will need different parts).
- Rivnut install tool
- 10mm Rivnuts x2
- M10 Bolts, 30mm length x2
- M10 Washers x2
- 20mm x 2mm x50mm iron plate to reinforce holes in bar
- 20mm x 10mm x 1m Aluminium box section
- 10mm drill bit
- Drill
- Loctite
Why Did I Use Aluminium?
Running a bar between the wishbones does lose a bit of ground clearance (the 10mm thickness of the box section). Nothing catastrophic but if the bar does hit something, I want the bar to fail first and not the subframe. I anticipate the aluminium will tear before any damage is done to the subframe. If the the brace were made from steel I think the story will be different. In addition to that, we only need the brace to be good in compression and 10mm x 20mm aluminium box section will be more than strong enough, in my opinion.
Issues
On this specific car there is a slight issue with the using a straight bar. The left side of the subframe is not parallel to the ground, it rises slightly as it goes towards the center. This causes the bar to bow upwards slightly if you fully tighten the bolts on the bar. Slackening of the bolts on the right side (and using Loctite) helps.
What’s Next?
I think I will be fitting a purpose made bar. The aluminium does a job and it showed me there are improvements to be had so fitting a dedicated steel item, which should be even more rigid should be worth the outlay.
