Folding Bikes - PBP on a Brompton

Hi all,

For those of you who don't follow BromptonTalk...

I'd like to tell you that I passed all 4 Brevets this year, and I've
qualiefied for PBP.
The Brevets were of 200, 300, 400, and 600 km.
PBP, if you don't know, is Paris-Brest-Paris, a cycling event of
1,200km that should be covered in less than 90 hours. It will happen
this August in France.

I did the 600km (actually a little less, but more than 560km) in 38
hours total, of which 27 hours were ride time.

A little about my bike:

It started as a S6R.

Major features and modifications:

*) Double chainring (using SP bracket) of 53/33T. The 53T helped me
keep close behind a stronger rider at speeds exceeding 45 km/h in
the flat.
Max speed downhill was 70 km/h (my max speed record is 79 km/h, with
Schwalbe Marathon tyres as well)

*) Standard Brooks B17 saddle

*) Ergon M2 grips

*) Shimano A520 SPD pedals

*) Schwalbe Marathon tyres (fitted new before the 600km ride)

*) Lights: Battery, Cateye HL-EL320 in front

*) Luggage: Rear rack, with Carradice Super-C rack bag.
No front carrier block and no saddle bag.
I used a bento box for keeping food handy during the ride, and also
my small triangular frame bag with most needed tools

*) Water: 2 1l Zefal Magnum bottles.
One on the handlebar post using a Zefal Gizmo,
and the other on the seatpost using Twofish Quick Cage


My Brompton is my only bike, and I use it for Brevets, weekend rides, commuting, leisure, etc.
The Brompton isn't the weakest link, it's the rider.

Tal.

Congratulations – I raise my hat high for your achievement!
I am interested in your gear range – what is the size of your rear bracket - 13 or 14? And do you have the original Brompton cranks – can you really fit a 33 bracket on it? I have a Merc and I am investigating options on how to fit a smaller than 39 second chain ring in front. I even tried FSA crank-set 34/50 with Mega-Exo bb, but unfortunately the axle length wasn’t enough – bike wouldn’t fold. Bottom bracket width should be for a road bike, but axle length for a mountain bike in order to be able to fold the bike.
And do you have bar-ends fitted? It would be very interesting to see some pictures of your bike. Thanks for your interesting post.

After much thought and consideration as to how to reply to your post, I have decided upon a one word response:


wow!

wow!

+1

Very impressive achievements! I love my Brompton M6L with the 12% lower gearing option for the San Francisco hills, but miss a nice top gear for use on the flats. I guess I need to look at converting to a double chain ring.

Thanks for a great post.

EDIT - Any chance you could post photos of this wunderbrommie? I'd really be interested in seeing some close-ups of the crank/chainrings/front derailleur set-up.

I have decided upon a one word response: wow!
I think I'll have to go with the slightly more verbose evaluation, namely:

"You're nuts."

:D

As frank our erstwhile Dog would say ,"I, BOw WOW! WOW!" Quite an acheivement

Wow +3 !!! have you considered entering Smithfield folding bike race (http://www.bikeforums.net/showthread.php?t=306303)..... that should scare the strida riders with shaved legs :)

Very Impressive, and it confirms my theory that one of the most important components that every single bike can upgrade is the rider. That's where most of the weight can be saved, most of the power can be gained, most of the performance can be improved.

Congratulations and good luck!


14R (happy to be able to ride 25 MILES on his Brompton)

Congratulations – I raise my hat high for your achievement!

Thank you.


I am interested in your gear range – what is the size of your rear bracket - 13 or 14?

As I wrote in my original post, it's Bromptons 13/15 cassette.


And do you have the original Brompton cranks – can you really fit a 33 bracket on it?

The whole drivetrain has changed.
My current setup:

Truvative 118mm BB (to be replaced by Specialites TA Axix Ti 116mm soon)

Specialites TA Vega crank arms, with 110mm spider (i.e. BCD.)

33T: Specialites TA

53T: BBB (Only one I know that makes 53T 110 BCD with shafts that help the chain climb it.)

Shimano 105 front derailleur.


And do you have bar-ends fitted?

The Ergon grips come with bar ends, yes.


It would be very interesting to see some pictures of your bike. Thanks for your interesting post.

There are (few months) old photos in BromptonTalk.
I should take new ones and will post there, and here as well.

Tal.

Wow +3 !!! have you considered entering Smithfield folding bike race (http://www.bikeforums.net/showthread.php?t=306303)..... that should scare the strida riders with shaved legs :)

That's for racers, I'm no racer.
Nor is my bike weighing at over 13Kg, with full randonneuring setup.

Tal.

I think I'll have to go with the slightly more verbose evaluation, namely:

"You're nuts."

:D

:lol:

Regardless, I applaud your iron butt.

-G

Congratulations – I raise my hat high for your achievement!
I am interested in your gear range – what is the size of your rear bracket - 13 or 14? And do you have the original Brompton cranks – can you really fit a 33 bracket on it? I have a Merc and I am investigating options on how to fit a smaller than 39 second chain ring in front. I even tried FSA crank-set 34/50 with Mega-Exo bb, but unfortunately the axle length wasn’t enough – bike wouldn’t fold. Bottom bracket width should be for a road bike, but axle length for a mountain bike in order to be able to fold the bike.
And do you have bar-ends fitted? It would be very interesting to see some pictures of your bike. Thanks for your interesting post.
I was just looking at mine today Maranen and I doubt that the Merc crank can take a smaller chainring than that one, hence they offer that as the lowest. Take a look at the ring from the left hand side of the bike and you'll see that the radius of the chainring bolts is pretty well near the 39 tooth ring. It's easy to see on mine since I already have the 52/39 setup working. To be honest, that setup gives me a low gear of about 39 inches, so I can get up most things. I wonder if it is possible to put in a SA 8 speed? From what they say in the DT mini thread, that gives a very low gearing at the bottom end, but I'm not sure how such a setup would fit. It may be wider than the srf-3.

I'm just trying to get my head around doing 560km in 28 hours.... That's an average of twelve miles an hour I think, but I've had wine, so maybe not. After riding the fully loaded Merc 40 miles in a day in moderately hilly country, I spent 14 hours lying in my jungle hammock listening to my personal radio and never felt the need to get out, except to pee. Even at my fittest, and years ago when I was forty, I once rode 380 miles in four days on a Dawes touring bike and thought I'd had a great adventure. Five hundred and sixty k is 350 miles I think.

14R is right, It is a rider upgrade that I need.

I wonder if it is possible to put in a SA 8 speed?

Supposedly, the big cog on the SA-8 is too big for the Brompton's rear triangle.

If you look at BromptonTalk, you can find the details there.

Oh, the SA-8 has a ~300% range; much wider than the SA-3.

-G

Tkatzir - Thank you for your answers. I've been thinking of what you did, and I must admit it's beyond my comprehension. Best I can do is about 100km a day. The bike setup is important of course but I guess one could say that you are the strongest link there. I can't express myself well in English but as a Finn I could say:"Perkele poika minkä teit!".

EvilV - I examined the Merc crank and came to the same conclusion as you. I even experimented with an old 39 chain ring where I drilled holes to be able to fit it to the crank, but it didn't feel satisfactory for steepest hills. I'm writing this in an internet cafe and time is running out.

Tkatzir - Thank you for your answers. I've been thinking of what you did, and I must admit it's beyond my comprehension. Best I can do is about 100km a day. The bike setup is important of course but I guess one could say that you are the strongest link there. I can't express myself well in English but as a Finn I could say:"Perkele poika minkä teit!".

EvilV - I examined the Merc crank and came to the same conclusion as you. I even experimented with an old 39 chain ring where I drilled holes to be able to fit it to the crank, but it didn't feel satisfactory for steepest hills. I'm writing this in an internet cafe and time is running out.
If you look carefully at this picture Maranen, you'll see what I mean. Check out the position of the chainring bolt you can just see through the frame at about the 11 o clock position. See how near the edge of the ring it is. I think you would definately require a different crank altogether to get a smaller ring.

http://img244.imageshack.us/img244/6452/dscn1209kp4.jpg



Supposedly, the big cog on the SA-8 is too big for the Brompton's rear triangle.

If you look at BromptonTalk, you can find the details there.

Oh, the SA-8 has a ~300% range; much wider than the SA-3.

-G

Thanks for that. It's a pity, although I do like the simplicity and efficiency of the srf-3.

Thanks for that. It's a pity, although I do like the simplicity and efficiency of the srf-3.

How much is the kit to add a front derailleur to the Brompton? And it works pretty well?

How much is the kit to add a front derailleur to the Brompton? And it works pretty well?

I was about to ask the price. If it is the same used on mercs, yes it works quite decently.

You go Tal !!!!

I bought mine from a guy on the Brompton talk list for £40. He had bought the clamp and mech for himself and never got around to putting it on his bike. I believe Steve Parry sells the clamp alone for £40. Then there is the mech which is about £15. The chap threw in a second hand friction lever and I bought a cable for £2. Then there is the front chainwheel. If you own a Merc, since it is made in Taiwan, and its parts are inexpensive, you can smile broadly and part with a mere £4.50 for the 39 toothed variety. Other wise, you might pay about £30 for one from a European manufacturer.

My entire conversion cost me under £50. It has made the bike more versatile by allowing a 25% gear reduction at the flick of a lever. On the Brompton Talk list at Yahoo, someone asked me why I hadn't used the full capacity of the mech by going for a 32/53 combination. The answer is I didn't feel I needed that much, but also that the crankset won't take a chainwheel smaller than 39. Check out the photograph taken through the frame to see why. The mounting bolts are as near the edge of the chainwheel as could be done with a 39 tooth wheel. If you want to get into new cranks, you can go as low as 32/53 with the mech I used.

The modification works brilliantly. It is totally reliable. One might ask questions about the ability of the chaintensioner to wrap enough chain to keep the tension correct, but I have had no trouble and only once had the chain jump off since I did the mod. This could have been due to other causes than the tensioners ability to cope with a smaller front chainring. I use the alluminium upgrade tensioner made by the Merc people.


PS I believe that Merc is a re-badging name for the Taiwanise flamingobike company. They seem to make a variety of qualities of Brompton lookalike, one with a horrid pressed allu frame, and other better ones like mine which I think is pretty good. They have upgraded their chain tensioners to all alluminium ones which makes me think they are the source of Merc bikes.

http://www.flamingobike.com/products/products_show.php?pid=29&cid=3

Today I rode 20 miles, averaging 15.6mph but following some roadies for about 4-6 minutes somewhere between 20-21mph. Even though I cannot blame the bike for not being able to keep up with them any longer, if I could crank rather than spin today I would keep up for another...minute or so :)

One way or another, I just haven't made up my mind if I need a bigger chainring or if I need a wider gear range (never faced a hill that I couldn't go up, but after all, I live in freaking FLORIDA!).

14R

PS: Now...the fact that folding bikes look really, I mean, REALLY good with expensive carbon fiber cranksets and a good quality chainring should be subject of deep meditation for now on...

I can manage 22 miles an hour downhill. Does that count?

Actually, my speedo shows a peak velocity of 31 miles an hour, I think I must have ridden off a cliff or something.

:)

Evil5,
31 miles is really fast, but can be achieved for a feel seconds (ok, for ONE SECOND) if you work really hard and don't have a lot of wind against you.

I decided that I will start with a new set of crankarms and a bigger chainring. SP clamp for front derailleur will be if (and only if) I feel the need or granny gears...

First of all congratulations.....
Now I would like to ask a few questions about your modifications;
since I am new in the forum and I didn't read the entire forum, could you please give me the complete list of parts that you use to install a double sharing. What about the bracket to change the speed on the sharing. The Brompton does not have any bracket itself.
Another question that I have is about adding some more gears to climb some hills. I've been thinking of a 8speed internal hub, but I heard the SA 8 speed hub made in China are not so reliable. I was thinking of a Shimano Nexus internal 8 speed hub. Have you heard anything about it?
I believe, besides the double sharing your Brompton is still a 6 speed, How was it on the hills?
Thank you very much for your attention.

Orlando

Hi EvilV,
Could you please tell the model of your Bike, and where did you buy it?

Thank you,

Orlando