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Old 07-26-07, 01:36 PM   #1
electrodyne
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Brompton weight: Steel vs. Titanium?

Obviously the all-Titanium Brompton will be lighter than a steel Brompton.

However, I've read postings and articles that seem to indicate the weight saving is only about 3-4 lbs at the most. This doesn't seem like much of a weight savings to justify a near $3K price tag.

Is the weight differences between the 2 models not that substansially different, or is it?

This also brings me back to a previous posting on how Leonard Rubin was able to get his Brompton down to 19 lbs. but that is another thread altogether.
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Old 07-26-07, 03:02 PM   #2
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1) Titanium bromptons are not all titanium. In fact, they're mostly not titanium. Only certain bits are titanium.
2) Your right, the difference is not that much.
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Old 07-26-07, 03:18 PM   #3
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Of course Makeinu's post answers the last question regarding Rubin.
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Old 07-26-07, 03:18 PM   #4
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Is the titanium Brompton--not Rubin's bike--really close to $3K?
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Old 07-26-07, 03:22 PM   #5
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Of course Makeinu's post answers the last question regarding Rubin.
Just to clarify. Is Rubin's Brompton all titanium or is it just that if you strip the steel Brompton down it ends up being about 23 pounds so shaving another 4 pounds by using titanium bits gets you down to 19?
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Old 07-26-07, 03:49 PM   #6
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Just to clarify. Is Rubin's Brompton all titanium or is it just that if you strip the steel Brompton down it ends up being about 23 pounds so shaving another 4 pounds by using titanium bits gets you down to 19?
I think that his prototype is now down to something like 17 pounds and is all titanium. Although that would depend on whether you are talking about the Rohloff model or the triple with 9 sp cassette in the rear.
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Old 07-26-07, 04:56 PM   #7
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An 'Extra Light' Brompton includes the following titanium parts: Rear triangle, forks, seatpost, folding-pedal axle and wire mudguard [fender] stays. The rest remain standard and the frame is always steel.

You can, of course go further and use a titanium railed or carbon saddle and weeny out on other parts - cranks and the like as well as lose the odd gram by swapping out steel bolts for titanium or alloy. Heck you can even get ti spokes these days - but none of these are offered on the Brompton 'stock' and these would be your own aftermarket upgrades.

The major parts they do offer give the following weight savings (My steel figures are based on Merc weights not Brompton but are likely to be very closely comparable), which isn't a massive amount lighter when you factor in the frame - but it's good to remember that most people want a light Brompton not because they want a racing machine but because they want it to be easy to carry when folded.
Rear Triangle:
Steel = 808g
Titanium = 455g
Saving = 353g (43.6%)

Forks:
Steel = 610g
Titanium =265g
Saving = 345g (56.6%)

Seatpost:
Steel = 475g
Titanium = 275g
Saving = 200g (42.1%)
----
Overall saving: +/- 898g
Merc frames are aluminium and a bit lighter than steel. (I don't have a figure on this weight saving but this is what I am doing with my project Merc/brompton hybrid: ti everything [forks, rear, seatpost, bollts], singlespeed, single brake setup with Ti Brooks B17, and no fenders, rack or any such paraphenalia)
I expect it to be rather light and easy to carry

Last edited by LittlePixel; 07-26-07 at 06:03 PM.
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Old 07-26-07, 06:07 PM   #8
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USD 3K? A fully equipped Ti (all Brompton options) 6-speed with S bars and rack with all add-ons comes in a little over $2K, that being a BeSpoke/ALC order (no fancy clear lacquer). The stock titanium lightweight models are much cheaper.

The carrying weight is the issue, as others have said.
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Old 07-26-07, 06:23 PM   #9
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Bicycle weights are deceptive - due to the frame being the major component, there is the perception that its weight dominates. It doesn't. It is perhaps 20% only. To get a really light weight bike, you have to pay attention to every little bit, starting with the major items - the wheels. Get the spoke count down, use butted spokes, light rims and especially light tyres. Use light hubs - some of those hubs are anchors. Not for the old BS saw of "rotating weight is more important", but because wheels are another 20% and weight is most easily saved there.
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Old 07-26-07, 06:56 PM   #10
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And mostly in the tires. But you can drop nearly a pound in the pedals alone. Speedplay pedals come in at 150gm.

Jur, how are the AC hubs holding up? I'm curious about the new bearing sets. Have you had a chance to seriously abuse them yet?
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Old 07-26-07, 07:08 PM   #11
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LittlePixel, thanks for posting the weights. I've seen it said here and various other places that the Titanium Bromptons are 3-4 pounds lighter, and that is an apples to orange comparison, because the Titanium bromptons are also equipped differently (e.g. lighter saddle and tires). For example, if you want the Marathon tires for reliable commuting, those are heavier than the Stelvios.

If you are looking at the gain for Titanium parts only, it's 2 pounds. That's it. I don't think that's enough weight savings to justify the additional cost, which is why I didn't do it.
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Old 07-26-07, 07:25 PM   #12
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Jur, how are the AC hubs holding up? I'm curious about the new bearing sets. Have you had a chance to seriously abuse them yet?
Yes, inadvertantly; due to the R20's BB issue I have had to commute with the Swift, and it turned out to be the wettest 3 weeks in years. I literally washed the bike twice a day! I have done somewhere between 1-2000km on the hubs, and in just 2 weeks completely wore out the brand new brake pads!

So the hubs have seen commuting duty which is heavy duty work - extra 10kg of luggage, bumpy bike track, wet, wet weather, mud, grime, grit, frequent washing, you name it. The wheels are still as true as when I built them and the bearings feel smooth. the freewheel is much louder, though. Better check it tonight.

I must say I am relieved since I have read some bad reviews about the AC bearings.
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Old 07-27-07, 04:22 AM   #13
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Originally Posted by LittlePixel View Post
....The major parts they do offer give the following weight savings (My steel figures are based on Merc weights not Brompton but are likely to be very closely comparable), ......
Rear Triangle:
Steel = 808g
Titanium = 455g
Saving = 353g (43.6%)

.....----
Overall saving: +/- 898g
....
Hi
Thanks for the numbers. I have read somewhere that Brompton's fork and triangle are made of chromo-molybdene tubing - it's a little lighter than Merc's steel tubing.
I also intend to replace Merc's fork and rear-triangle with ti-parts.
I already have the ti-seat post, but before buying the ti-fork and ti-triangle I would like to be sure that the parts are interchangeable. I mean that it would not be nice to find out that I have to file off some 0.5 mm somewhere - that would weaken the structure. So - has anyone made it and succeeded?
And is there any special method to paint the ti-parts?
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Old 07-27-07, 07:19 AM   #14
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Yes, inadvertantly; due to the R20's BB issue I have had to commute with the Swift, and it turned out to be the wettest 3 weeks in years. I literally washed the bike twice a day! I have done somewhere between 1-2000km on the hubs, and in just 2 weeks completely wore out the brand new brake pads!

So the hubs have seen commuting duty which is heavy duty work - extra 10kg of luggage, bumpy bike track, wet, wet weather, mud, grime, grit, frequent washing, you name it. The wheels are still as true as when I built them and the bearings feel smooth. the freewheel is much louder, though. Better check it tonight.

I must say I am relieved since I have read some bad reviews about the AC bearings.
That's good news. It sounds like they've addressed the problems with the new hubs. At a minimum, the bearings are now easy to find. My rear dropout is 135mm, so I was tempted to go with their mountain hub, but got cold feet since I tour in places that would not have parts available.
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Old 07-27-07, 07:56 AM   #15
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That's good news. It sounds like they've addressed the problems with the new hubs. At a minimum, the bearings are now easy to find. My rear dropout is 135mm, so I was tempted to go with their mountain hub, but got cold feet since I tour in places that would not have parts available.
For touring, I would also not choose AC, but plain cup-n-cone hubs, say XT. My AC wheels are for going fast up mountains. Or trying to, at least.
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Old 07-27-07, 08:58 AM   #16
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Re saving two or three pounds:

But what's the point? The bike with me on it weighs almost 190 pounds. Would I really fly if the all up weight was 187?

This quest for weightlessness seems nuts to me. I probably go about all day with three pounds of junk about my person.

Alternatively, we could all cycle further, lose three pounds and be wealthier and healthier too.


Just my quirky opinion. Pay no attention and spend lots of cash instead.

Last edited by EvilV; 07-27-07 at 11:06 AM.
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Old 07-27-07, 12:44 PM   #17
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Re saving two or three pounds:

But what's the point? The bike with me on it weighs almost 190 pounds. Would I really fly if the all up weight was 187?

This quest for weightlessness seems nuts to me. I probably go about all day with three pounds of junk about my person.

Alternatively, we could all cycle further, lose three pounds and be wealthier and healthier too.


Just my quirky opinion. Pay no attention and spend lots of cash instead.
I'd have to say that I agree that it makes relatively little difference, except unloaded up a long, steep climb in a fast group ride. (I can usually keep up with the team riders until the ascent. At that point, I routinely get dropped, and there is just a 5 pound difference between their carbon bikes and my folding bike.) But folding bikes also have to be carried! I don't think many people do fast group rides on Bromptons, but a lot of folks have to hoist the machine up flights of stairs.

Also, a lot of folks love the Marathon Racers, and I agree that they are great touring/utility tires. But try to go fast on them, and they make a lot of noise.
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Old 07-27-07, 02:46 PM   #18
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Yes - of course when carrying a bike, weight is important, but I feel you'd need to take several pounds off to make it much easier, and as we know, that is very expensive if the thing was reasonably engineered in the first place. If I have to carry my Merc, I like to carry it in its ready to ride mode, because if I grasp the main frame above the pedals, it balances beautifully. Folded it is somewhat less convenient to lug around.
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Old 07-27-07, 05:41 PM   #19
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The two pounds saved is least noticed when the bike is ridden. But for the times when it is folded and must be carried, or when folded and must be shipped in luggage, two pounds can be more important.

If I had to carry my folded bike up four floors every day, I might regret the extra expense a little less.
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Old 07-27-07, 05:47 PM   #20
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While I agree that a kg or so won't make all THAT much difference riding, the big thing I notice is my 9kg Swift feels far more nimble, and it is therefore such a pleasure to ride. Admittedly, the diffs between my Swift and my R20 is a massive 8kg, so that is like comparing apples to elephants.

Still, I wanted a light bike because I already had a heavy one.
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Old 07-27-07, 06:34 PM   #21
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I don't know why Brompton had to resort to an expensive alloy (Ti) to reduce weight on their bikes. However you can break the 20 lb barrier and Dahon did it with their Presto Lite (discontinued) made of aluminum.

As for under 20 lb folders, you don't go faster. My 25 lb Presto was just as fast as a 19 lb Presto Lite because the gearing was exactly the same. In addition, you will not be able to carry a 20 lb folder for more than 1 city block before it wears you out. The only advanage a 20 lb folder gives you is the ability to lift it with ease.
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Old 07-28-07, 01:35 AM   #22
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An aluminium frame won't meet Brompton's durability standards with the current dimensions and will increase the size of the fold if beefed up.
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Old 07-28-07, 05:40 AM   #23
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Quote:
Originally Posted by maranen
Thanks for the numbers. I have read somewhere that Brompton's fork and triangle are made of chromo-molybdene tubing - it's a little lighter than Merc's steel tubing.
Yes - this is why I qualified my figures in case of disparity

Quote:
Originally Posted by maranen
I also intend to replace Merc's fork and rear-triangle with ti-parts.
Good idea!

Quote:
Originally Posted by maranen
I would like to be sure that the parts are interchangeable.
Yes they are - I'm in the very midst of this right now and have not come up against any problems whatsoever.

Quote:
Originally Posted by maranen
And is there any special method to paint the ti-parts?
But that will add weight! And they look so nice in raw Ti!
But yes - perhaps you don't want people to know they are Ti - so it's not a bad idea - Powder coating shouldn't require any special treatments; painting either, though one probably shouldn't use acid-etch primers that are intended for steel.
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Old 07-28-07, 05:42 AM   #24
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Originally Posted by EvilV
But what's the point? The bike with me on it weighs almost 190 pounds. Would I really fly if the all up weight was 187?...Pay no attention and spend lots of cash instead.
I thought this thread had already clarified most people's reasons for lightening their brompton was for the carrying of it when not riding rather than weenyness in the saddle.
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Old 07-28-07, 06:33 AM   #25
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I thought this thread had already clarified most people's reasons for lightening their brompton was for the carrying of it when not riding rather than weenyness in the saddle.
It isn't mentioned as a reason by anyone but you and Chenry Huw, and then only in passing. Weight features massively in the promotion of all kinds of bikes and in non -carried bike discussions. For a lot of people the search for the ultimate feather weight bike has become a sort of search for the Grail, whether they carry it around or not. I suspect that a lot of perceived improvement in light bikes is as much a matter of placebo effect as anything else. Of course there are nice responsive bikes and absolute dogs, but I doubt that a pound or two here and there is the defining difference between them.
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