Brompton - substituting a 2003 rear wheel. Any issues to expect?

muzietto

New Member
Location
Cagliari, Italy
I must put a new rear wheel in my 2003 Brompton. I have found a potential substitute online.
My doubts are:
- can the 2021 rear wheel fit in the 2003 frame?
- is the size of the 2021 rear wheel exactly the same as in 2003, or do I have to purchase a new tyre?
- is the excursion of the little chain of the gear system the same as in 2003, or do I have to put a different lever on the steering wheel?
I hope someone can answer my questions.
Cheers.
 

T4tomo

Guru
the good thing about bromptons is the frame has barely changed in years (it got a little bit longer at some point (pre 2000?) and most upgrades are backwards compatible.

so on wheels -sizes are identical and it will fit in the frame, assuming your "substitute" will fit the current 2021 brompton, whether it is a genuine brompton wheel or not.

the final question depends on what hub gears were/ are is fitted to the old wheel and the new wheel -
a brand new hub gear should come with the little indicator chain and lever,

if it doesn't have the lever, the existing one might work - if it is a 3spd, if not a replacement to match your current hub model should be available on line. SA SRAM etc have marginally different pull ratios so you really need a lever compatible with the hub, not just any old 3 spd lever, although some will work cross brand.
 

berlinonaut

Über Member
Location
Berlin Germany
the good thing about bromptons is the frame has barely changed in years (it got a little bit longer at some point (pre 2000?) and most upgrades are backwards compatible.
The change of the frame hinge and in consequence the wheelbase was in 2004 with the invention of the MK4. The OP's bike dates from 2003 and thus is a MK3 with the shorter wheelbase.

so on wheels -sizes are identical and it will fit in the frame, assuming your "substitute" will fit the current 2021 brompton, whether it is a genuine brompton wheel or not.
The Brompton rear frame has an OLD of 112mm whereas "normal" bikes do have 130 or 135mm (and even more with some modern MTBs and Fatbikes). So it is relevant to buy a substitute matching for a Brompton, not jus a "genuine wheel". Rim size did not change - ETRO 349 from the beginning until today.

the final question depends on what hub gears were/ are is fitted to the old wheel and the new wheel -
a brand new hub gear should come with the little indicator chain and lever,
A 2003 Brompton does have a SRAM hub whereas today Brompton is using S/A only. In case it is a six-speed the dreailleur part will work, for the hub gear part you will need a different toggle-chain and probably a new gear cable as well (as the long nut on the gear cable is different). I am however wondering about the need for a new rear wheel: The Sachs/Sram hubs are pretty much bombproof - barely ever one is beyond repair or needs a repair at all. In case of trouble: Here are loads of technical documents for Sachs hubs (in German) - they should in principle apply to post 2000 SRAM hubs as well.
If it's just the rim that is worn it is cheaper to respoke the wheel with a new rim than to buy a new wheel.
 

berlinonaut

Über Member
Location
Berlin Germany
3 speeds are so unfussy that Brompton made one lever to work with either Sachs or SA.
From 2005 on, the OPs bike is older than that and thus using a SRAM lever if in factory state. I would assume that it will also work with the S/A hubs but did not try it myself and some people on this very forum were doubtful about the idea.
 

berlinonaut

Über Member
Location
Berlin Germany
I must put a new rear wheel in my 2003 Brompton. I have found a potential substitute online.
My doubts are:
To quote your from your post in another forum where you put the same question:

My bike has 2*3 gears and the new wheel is meant for double sprocket. I'll just move the sprockets from the old to the new bike.
I would not know which model is my bike. The baggage rack on the back has a shape that is no more present in current models.
About the excursion of the little chain of the gear, I understand my Sturmey Archer gearbox is no longer utilized, so reckon I will buy a new set of levers for the handlebar.
If you do habe a 2*3 it ist indeed a post 2002-bike. But the fact that you are talking about a Sturmey gearbox makes me wonder: The 2*3 was using an SRAM gearbox from the beginning until 2009, so something seems to be wrong here: Either the claimed age of your bike or it has already got a new rear wheel. Also you cannot move over the sprocket fromt the old to new rear wheel as SRAM and S/A BWR sprockets are vastly different. Lastly your statement about the baggage rack makes me wonder: While differnces to actual bikes are there they are not that huge.
So to gain safety a couple of pics of your bike would be good, maybe along with the frame number. Plus you still did not mention why you want to swap the rear wheel.

But judging from the fact that you did post your question to multiple forums simultaneously and did not bother to check back for answers here we possible face another "hit and run" poster and could better do other things with our time instead of answering hit-and-run-questions...
 

rogerzilla

Legendary Member
The SRAM hubs are getting tricky to support now due to NOS parts drying up (blame SRAM for deleting the entire IGH product range in 2017).

In terms of consumables, you can generally refill ball cages with new ball bearings, or even use loose balls, but a snapped axle key, the T3's weak point, will really ruin your day as the bike will not even freewheel. The keys are like hen's teeth, and have gone up in price 7x in the last few years as they run out. Supposedly you can file an SA key to fit, and use an SA indicator and cable anchorage.

The other incredibly rare SRAM-related item is the 15T derailleur sprocket. A normal SA 15T 3/32" doesn't have the intermittent half-height teeth needed for easy shifting.

The point is that fitting a newer rear wheel has some advantages!
 

rogerzilla

Legendary Member
doing a Google search of"axel key/toggle chain/sram hubs" you can get one off eBay for £2.79 if that helps anyone ... :hello:
That's a toggle, not an axle key. Toggles are easy to come by. This is an axle key (from my T3). The metal is very thin around the threaded hole, and they sometimes just snap in half. Clumsy shifting (trying to force a lower gear when the bike is stationary) is a contributory factor, but it is a weak design.
 

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Tenkaykev

Veteran
Location
Poole
That's a toggle, not an axle key. Toggles are easy to come by. This is an axle key (from my T3). The metal is very thin around the threaded hole, and they sometimes just snap in half. Clumsy shifting (trying to force a lower gear when the bike is stationary) is a contributory factor, but it is a weak design.
That looks like something that would be pretty easy to make. I no longer have access to an engineering workshop and the wealth of metal stock and tools I once had but it seems a straightforward job.
 

rogerzilla

Legendary Member
Possibly. It's a half-round shape so could probably be filed down from a steel rod of appropriate diameter. Given the added complication of drilling a hole in a rod not much bigger (which is the source of the problem!) and tapping it to the right thread, it is probably easier to modify an SA key.
 
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