Birkin XS - side by side comparison to a Caterham CSR

[Croc]

Yesterday, I put my Caterham CSR next to Tom Carlin of Birkin USA's brand spanking new Birkin XS to compare and contrast the two. Very interesting exercise that prompted debate on which company got it right.

 

First up is the front view. My car is a 2010 kit built 2011. I am flattered Tom copied my paint scheme!

 

 

 

The photo is deceptive - it appears the CSR is lower nose height, bonnet height etc, but it is not - maybe a fraction of an inch but the difference is optical. Headlights clearly are lower. CSR has the carbon double chin which visually lowers the look for aero. The Birkin has a different profile intended to reduce lift - looks far more integrated as a unit than the Caterham. Width of front track is about the same.

 

Yes I know the CSR is running directional tires backward - in CR500 it gives better grip plus it evens out the wear on the Lightning track from the bowl.

 

Side on to the Birkin - this shows cowling and bonnet height are pretty identical. Wheelbase is same length (or close enough to not be noticeable).

 

 

 

Now side on for the Caterham. Steering wheel in the Birkin is closer to the driver. That could be because the Caterham has the swoopy dash which uses a Rover Metro steering column which differs to the regular dash. I prefer the higher wheel height of the Birkin - the Caterham wheel is too low.

 

 

 

Cockpit of the Birkin XS

 

Edited April 20, 2019 by Croc

[Croc]

Cockpit of the CSR

 

Not really a fair comparison as the CSR cockpit is not the standard one. I would like to see a 6 speed in the Birkin though. Can it take a Caterham 6 speed? Is it even worth it?

 

I prefer the Caterham seats to the Birkin but quite frankly you can put any seat you want in the cars to suit your personal taste. Both cars are easy to customize.

 

Birkin front suspension. The headlights include daylight running lights and indicators. Much cleaner design and look.

 

 

CSR front suspension - ok its got inboard shocks but does that make a notable difference? We did not do back to back drives to compare unfortunately as time got away from us.

 

 

 

Comparison of engine bays - the Birkin XS. What it does not show is there is a ton of room on the other side for a turbo charger. this is the 2L Duratec. The Caterham has the 2.3L Duratec. The purpose of this comparison is not for power contest but to compare packaging. Very similar layout and placement of chassis bracing. The CSR has a nose duct to take the airflow out of the radiator as it supposedly improves aero. The problem with this approach is that the engine bay becomes a closed cell which pumps hot air down the transmission tunnel and superheats the chassis tubes next to the driver. The regular Caterham matches the Birkin XS and I think the simpler approach is better in this instance.

 

 

 

 

Edited April 20, 2019 by Croc

[Croc]

Engine bay of the CSR

 

 

One thing on the CSR that I feel could benefit the Birkin XS is some form of cold air intake. I lowered the CSR intake temps by 30 degrees by adding a scoop to the side of the bonnet next to the air filter. Easy fix to make.

 

One thing I just realized I forgot to check - is the Birkin XS dry sumped or wet sumped? Tom can chime in on here when he gets back home. He is probably somewhere in Ohio heading west right now.

 

Now the next bit is where the surprise kicked in for both Tom and myself - look at the rear end differences

 

 

 

 

The CSR has far more rear end height than the Birkin XS. The chassis on the Caterham is definitely higher - the style is more horizontal whereas the Birkin slopes down towards the rear. But the ride height is much more on the CSR. Both cars are standard chassis set up - nothing special. I have the CSR on its original 15 inch wheels with Avon CR500s. Both are IRS cars - which is why I wanted to do this comparison.

 

The theories we chewed around with for such a significant difference were:

1) Birkin deliberately styled it this way to avoid any copyright issues given the earlier litigation between Birkin and Caterham

2) The CSR uses early 90s VW Passat rear end components adapted to fit to give it IRS. Could this be of such a height that they had to style the CSR this way? Really should have put my regular SV next to the two to confirm this idea.

 

The roll bar on the CSR looks higher but that seems to be just because the car sits higher.

 

Another observation is that the rear wings on the Birkin are wider than the CSR but the tires are narrower. So looks under tired at the rear end. I prefer the meatier look of the CSR tires. Tom said you could go wider on the back tires but then you had to go up a width on the front. Pretty easy fix to make and probably worth the time to do so if you were tracking the car regularly.

 

Tom was talking about a new engine option which will provide 300+ hp in a very clean installation. That is a game changer for going one up on Caterham power options. I will let Tom announce that one - very exciting news.

 

In my scrutiny of the Birkin XS I will say I was very impressed. Fit and finish were excellent. Tom clearly puts together an excellent car. It went very well on track and sounded great. I followed it on track to observe and it was steady, stable and smooth in the high speed corners.

 

I am not sure of the price but if you were to buy a CSR today and put a similar engine spec of the Birkin XS in it your price tag would be roughly $100k - double the Birkin XS. Is a Caterham CSR worth double a Birkin XS? No way in my view. If I had to buy a seven today that was wide body, has independent rear end, traditional looks, good quality then I would choose the Birkin - no hesitation. That saving of roughly $50k could be used for any number of other toys or keeping the better half happy. You could bling it up with carbon for another $10k and still have virtually the same car as the CSR for a $40k saving. Is a Caterham badge worth $40k - I don't think so. That Caterham price premium disadvantage kills any Caterham advantage in resale values.

 

I think Birkin is on a winner here with their XS model! I wish I had time to try it out on track.

Edited April 20, 2019 by Croc
added text

[wemtd]

Mike, as Tom(yellowss7) pointed out: they need company.

These two could be siblings separated at conception.

I think the csr will be lonely without this XS next to it in your garage

Edited July 7, 2015 by wemtd
Too many Tom's this year

[Kitcat]

I had a number of chats over the 3 day NJMP event with Tom, who incidentally, is a world class nice guy. As I have learned the hard way, who assembles the car is as important as who manufactures it. Tom clearly takes pride in producing a well constructed product. His car ran flawlessly over the two track days.

I owned an IRS Duratec powered '09 Birkin for 2 years and though it was still the latest iteration. Tom says no, there were many changes in the design of the Birkin XS and those have now found there way to the stock Birkin S3. Maybe he can elaborate.

An interesting tidbit is that Birkin manufactures all of their components, Caterham farms theirs out. So the body, chassis, etc., are all constructed elsewhere by others to Caterham's spec, and shipped to Caterham for use.

Finally, Tom showed me a photo of a new 'Vette and said it was owned by his 83 year old mother! He built a bike rack for it so she could carry her carbon fiber bike when she traveled. My kind of mom:).

[Kitcat]

Whoops, somehow ended up back here. Plz ignore.

Edited July 7, 2015 by Kitcat

[lucky dawg]

Mike - Is there any significant weight difference between the two cars?

[Croc]

Oops - should have mentioned that. Fairly close in weight. Mine with windshield on (instead of aeroscreen) and with side screens and full tank of gas no driver is 1325 pounds. Tom mentioned a number of approximately 1300 pounds for the Birkin in the configuration shown above. I don't know if that included a full tank of gas. The CSR is quite heavy compared with a regular Caterham due to the weight of the Passat IRS. That said the IRS delivers back more in performance in my view compared to the De Dion.

[MightyMike]

Both are beautiful looking cars.

[papak]

I picked up my XS kit at Tom's shop in Vail. Great guy and the shop is full of interesting stuff. He has been nothing but gracious and accommodating in fielding all of my dumb questions. The construction manual is pretty thin so I have certainly had my fair share. The only items that I have upgraded are some of the hardware. I am building mine with a mild 2.3l Duratec and a Subaru R160 LSD diff.

 

As to the weight issue, I have a Caterham exhaust in the shop and I guess it weighs maybe 20 lbs. more than the Birkin setup, mainly due to the heavier gauge tubing and larger muffler.

[Kitcat]

I think Tom told me the XS was around 1350-1375 lbs. Not sure if that was with a top, gas etc. When I sat in it the new seats were a huge improvement over the customary Birkin torture seats. The extra room was VERY nice also. It is still a small cockpit tho. Maybe a bit bigger than a Miata, maybe the same. More room for one's feet in the foot well.

[Ferdl]

I've read that the "Uprights offering 2 ride height Options".

How does this work? Pics?

 

Regards,

[Tbox56]

It was very interesting doing the side by side comparison of the 2 cars. I remember how impressed I was with Mikes CSR when he was in Colorado doing a shakedown prior to delivery, thinking wow that is the ultimate 7. It is quite nice to hear Mikes comments. I will just follow up on a couple of items.

 

The 2.0 liter in the Birkin has a Raceline wet sump which by the way I never saw loose oil pressure even in the punch bowl. In the past I have seen slight blips in pressure with these. We also offer an install kit for the 2.3 liter Duratec without lowering the engine.

 

The XS weight is 1285 with the windscreen, spare tire carrier (no wheel or tire), no driver, no fuel but all other fluids. This is only a 35 pound increase over the std S3.

 

Yes the uprights offer 2 ride heights, the std height and 30mm lower. The core upright is the same at all 4 corners of the car. The steering arms and some of the ball joint attachment points bolt on to the core upright. The wheel bearing is off center up and down this allows the upright to be flipped over and achieve the lowered ride height. However there is no practical way to drive on the street with the lower setup, it would be for track only. I will post some pictures in a followup post.

 

Tom

[Croc]

Ping for the gentleman who PM'ed me regarding fixing the photos in this thread

[papak]

My XS ended up at 1337# with driver, basic fluids, mounted spare and 6 gallons of gas. With the 2.3l Duratec and the factory skid pan, I have exactly 2" of ground clearance. I just finished installing a cold air box over the trumpets. I had an old "sausage" filter with worn-out foam. I removed the foam and glassed the SS wire frame, forming a 3" tube on the front end. A flexible duct with a foam "sock" type filter runs up next to the radiator. Less induction noise but a bit more power. Now I notice the exhaust note more.

[kayentaskier]

Mike,

Thanks for calling me a gentleman ...

Jim