Widening a C63

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Active Member
Sep 22, 2014
West Sussex
C63 Supercharged
Hi group!

it’s been a long time since I’ve posted here. I moved over to the FB group and the US forums for some information I needed and I forgot to come back. Anyway, I thought I’d post up a fairly major update to my build touching on all of the pieces which may help any of you with any of the parts you may be considering adding to yours.

First things first, if you want you car looking or performing anything close to what you see then you’re going to need money. If you’re worried about MPG or resale value then some or all of this is not for you but the beauty is you can pick the parts that suit you and your budget. Compared to some, I’m actually on the cheaper side of things . I won’t post costs as each retailer reserves the right to provide discounts and change their prices as they need, but I have had some good deals.

Here we go, I just want to say how happy I am with the way it has turned out. This statement is complete controversial but, I think I might like the way it looks better than a Black in a less-is-more kind of way; it’s a little less fussy to my eyes, and looks just like it would have if AMG had imagined a standard C63 wide rear. The dream was mine but Golding Barn Garage made it a reality; I could not have picked a better shop to carry out the work. Think of those US hot-rod shops that have TV shows on Discovery, that take so much care and attention with their work and who won’t let a car go until it is perfect, well, this is one of the UK’s equivalents. They treat each and every car as if it were their own, and expect that each build represents them as a company so, they won’t let anything go that isn’t done just right. They themselves I think are equally as ecstatic at the result which is shown to great lengths in their aftercare service. Already today they’ve been in contact to see how the drive went, what my thoughts were after a good sleep and if there are any issues. It’s also booked in for a 6wk checkup where they will go over everything to make sure it’s all perfect and thereafter be called upon in events they hold throughout the year. So, the duty is on me now to keep it in perfect condition.

Shortly before coming home and starting to write this, I passed an E92 M3 which I’ve always thought looked great. Well, my car now makes one of those look like a total wimp, so yay for me .

I’ll start with the most recent additions which are the coilovers, wheels, tyres and of course those pokey arches.

The Coilovers are produced by H&R and use Bilstein shock absorbers. I purchased these from Surrey Tuning who were fabulous, right down to hand delivering them to my door as they knew I needed them for the build I was doing. Their prices are great and they are among the friendliest and most helpful parts suppliers I have used so, thank you Chris and Dan (who also has a C63). The coilovers themselves I have so far found to be very nice. The ride is very much like standard, just a little stiffer damping wise but body roll is dialled out A LOT. Left to right transitions remain flat and the car less unpredictable feeling, albeit I need more time to give a full assessment. So far so good, and in my opinion if your car will only see occasional track duty then these are a great place to stick your money. Height wise, it may settle a little more but if it does I will likely raise it to where it is now or a touch higher. Ground clearance is actually ok, and the stiffness of the suspension stops it slapping the floor under rebound I’ve found. I can clear the ramp into my driveway, the three speed humps down my road but, I will have to be cautious elsewhere I don’t know I think, and I’ve already nearly forgotten that twice now which could have ended badly.

The wheels are JR Wheels JR30. I needed a set of wheels that I could get hold of quickly, weren’t ball-bustingly expensive given the cost of the rest of the build, but we’re also good looking, customisable, not too heavy and well made. Ticking all of that was hard but my hours on Google lead me to them and Driftworks as they supplier. Again, Driftworks were great. It took me no time to order, I picked my offset, Center bore and stud pattern and I was done. In under 2wks I had the wheels, finished in a satin black and looking mean. I think I made the right choice in terms of style but perhaps next year I will trade for something fully forged. The specs are 19x8.5 ET30 at the front and 19x11 ET35 at the rear and are wrapped in Michelin Pilot Sport 4S tyres which in my opinion are the best performance tyre on the market that isn’t geared towards track use. Even on the narrower wheels they made a huge difference compared to the OE Continental tyres. Now, I had to be cautious when ordering the rear due to this being a custom build so, I went with an offset that would work in any event. It turns out that I could have gone more aggressive yet and an ET25 will fit, as today I have stuck a 10mm spacer in there and I’m good. I could actually get a 12” rim in there now but likely what I’ll do if I go Forged is order up 11.5” and stick a 315-325 wide tyre in there. I could also reduce the front offset a little and use a 9” wheel, tyre width would need to remain at 245 or 255 max though.

The arches were something on my mind for a long time. I love my car more than any I’ve owned but coming from cars that handle precisely I was fed up, despite a diff, of having a car that needed feathering so much in corners and that likes to blaze tyres from a standstill with little effort. This sort of stuff is tremendously fun of course but after adding 100hp more to my car it became worse and started to be a little bit annoying at the times you just want to chill. I wanted overall the car I had but that could also handle, and of course, didn’t look so odd being so narrow at the back. No doubt, even with a narrow rear end, the standard wheels and quad tips work to make it look big and mean, but the longer I looked at it (I’ve had this over 5yrs) it started to look more and more inadequate back there. So my research took me to one place and that was HMS tubing who offer a wide arch kit. I initially really liked it but the more I looked at it the more flaws I saw in the overall look as it didn’t look OEM at all and it is mega expensive. All looked lost but eventual my i happened across HOC Dynamics, a Moshammer company who are a well known Porsche tuner in Germany. They offer a kit for saloon and estate only though so I had a choice of either leaving my idea alone or changing the saloon kit and stitching it together to make a custom coupe kit. The rest is history and the result is now that my rear end is just over 10cm wider in total. I went to GBG with one requirement and that was that I wanted the car to look factory. I can’t deny it looks anything different than what I wanted, in fact it has exceeded my expectations. I genuinely think that unless you know a C63 (standard) didn’t come with a flared rear, you’d never know. Looking under the arch it’s hard to tell what was factory and what is new as it looks seamless in there too, finished off with modified BS liners. Right around the arch from bumper to skirt you literally cannot tell what was added. The giveaway that this car is modified are the hugely wide wheels and low stance. I think if I put it up to stock height you’d struggle to know even further if you weren’t a car person.

The rest of the package was done throughout the previous 5yrs which I have all reviewed individually as time has gone one but, I’ll do a quick summary:

Front Splitter - Unit 17 Vorsteiner style splitter. These guys were great, finally I’d found a UK manufacturer of carbon fibre for the W204. Everything was spot on from shipping to fitment. It fitted like a glove.

Rear Diffuser - Xtreme Carbon UK. An easy eBay transaction here. Fitment is good and at the time was the only UK company I could find who did the style I have. I may however change this for the Unit 17 Big Fin version soon now that the overall look of the car can pull it off.

Interior - Lots of carbon overlays courtesy of eBay. Most have been very good and fit very well. I’ve also added a couple of subtle AMG emblems in there, again from eBay.

Exhaust - IPE catted headers, mated to standard resonator-back exhaust. Purchased from MSL. You don’t need me to tell you how professional they are, and they delivered on these for sure. A couple of years on and they’ve weathered well, and I’m also glad to say sound wise have deepened to a wonderful tone. At first they were brutally loud!

Engine - I have been through V5, V6 and V7 Eurocharged tunes. I have nothing bad to say about these at all, in fact my car is producing a healthy 553hp on the last map sent to me by Jerry. I purchased the My Genius from MSL, again who were superb. The difference between a 460hp standard C63 and one with just a remap is staggering. If you haven’t done it, do it!

Air intake shield - This I have myself to thank for. I made my own intake shield to divert cold air through the radiators and the result has been slower climbing oil temps and dramatically falling oil temps when it’s hot in there. There is member in FB (also on here) now making these for sale so please contact him for orders.

Differential - I already have the AMG differential but, if you don’t have one at all, get one installed ASAP. My personal favourite is Wavetrac but there is also Quaife.

I think that’s about it, other than the regular maintenance and cleaning I give it to keep it in good shape. In summary, it’s now time to enjoy my car and learn it all over again. It drives the same but different, in a good way. It feels like it’s limits are now much further away than they were before, so I need to find out where they are and play within them, albeit at a faster pace than I could before. There are a couple of minor issues though which are:
  • I have no idea where the rear end is now in relation to curbs, so I’m already freaking out about knocking a wheel on one while parking.
  • The rear end is now wider than the front and it JUST fits in the garage. Getting it out again is going to be butt-clenching.
  • I have become super precious over it. It’s been out 5mins and already it’s drawing attention. Anyone who looks at it is automatically a suspect and I give them evil looks.

The future looks like this.

  • Add carbon side skirt fins to match the splitter and diffuser
  • Add supercharger, likely ESS
  • Head to the Nurburgring






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Sorry, there are some spelling errors in this but I am not able to edit the post for some reason. Hopefully you can make sense. The name of the arch supplier is HPC Dynamics (not HOC).
Congratulations, the car looks wonderful. That rear quarter in the coupe always looked underdeveloped to me and you perfected it without going overboard. What is the wide arch made out of?

PS. It reminds of a member's Black Series but without a scratch. He knows ;-)
That really does look special :thumb:
A true labour of love and lolly!

That view, rear on, is just presence.
Must be tight on some narrow lanes though :confused:

Still, looks the mutts nuts :cool:
Struggled to appreciate the difference from standard at first, which shows how just well it's been realised. I had to put a stock picture alongside to get the full effect. :thumb:
Looks absolutely gorgeous.

But I don't know how you deal with a wider car in daily driving. They're already inconveniently wide.

Even my stock 2019 C63 causes me daily headaches with the aggressive London road furniture: crazy humps, super narrow ramps with concrete middle dividers in parking garages just waiting to take a bite out of my rims and side skirts and ridiculously narrow 6'6" width restrictions that I don't even dare to go through as they leave just a couple of centimetres on either side of my wheel rims....every day it feels like some crazed London bureaucrat with a beef against cars is cackling fiendishly in his cubicle while cooking up his next diabolical scheme. If I were driving your car I'd probably fear even taking it out of the driveway.
WOW! Cozy, what an epic and
very interesting and informative write up, love what you've done to your car
and it looks fantastic! :D:D:D:D
I for one lose a lot of B road enjoyment because my w205 is so wide compared to my e46 m3 which can scurry like a rat through a tiny crevice. The 204 might be a bit more sensible in terms of width vs the 205. I tend to get mildly to moderately annoyed at not fitting properly on narrow lanes, but thank goodness I didnt buy an RS6 or e63, that would really ruin my b road driving experience!

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