Anyone converted a mid-‘70’s Motobecane Mirage to 650b?
08-03-18, 01:04 PM
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Anyone converted a mid-‘70’s Motobecane Mirage to 650b?
I suspect the brakes won’t reach. I did some rough measurements which seem to indicate that I’ll need brakes with 90mm - 100mm but I don’t have a 650 wheel on hand to try it.
If anyone has attempted this please let me know if it worked or failed!
If anyone has attempted this please let me know if it worked or failed!
08-03-18, 01:38 PM
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...addicted...
Hold on a sec...
08-03-18, 02:06 PM
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Well, I happen to have those things in the garage, here are some pictures.
Set up for 27" wheel:
Bottom of travel original brake.
MAFAC Racer, bottom of travel
I think you need at least 90mm of drop from the bolt.
Set up for 27" wheel:
Bottom of travel original brake.
MAFAC Racer, bottom of travel
I think you need at least 90mm of drop from the bolt.
08-03-18, 02:36 PM
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You could probably make it work with some sort of drop bolt solution. As an example, here's something I did to get extra reach on the rear brake of my Sequoia when I was experimenting with using 650B wheels on it.
I think that got me around an extra 20mm of drop -- as you can see, more than I needed.
I think that got me around an extra 20mm of drop -- as you can see, more than I needed.
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08-03-18, 04:13 PM
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That's a lot of reach. If you found a pair of calipers that could do it, I suspect it would feel pretty flexy and not reassuring.
Having canti brake posts brazed on would be a good solution if you were really attached to the frame, but I'd probably just settle for good fat tires on 700C rims.
Having canti brake posts brazed on would be a good solution if you were really attached to the frame, but I'd probably just settle for good fat tires on 700C rims.
08-03-18, 04:24 PM
#7
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First get a real measurement. Presumably you have some kind of wheel on hand? If you have a 27x1-1/4 wheel measure brake reach with that and add 23mm. If you have a 700c wheel add 19mm.
Weinmann 900 will reach your guessed at measure. Not common but not at all hard to find. Just do a google search and see all the for sale hits. Cheap too. A good brake that very few want.
Please do not bet your life on a homemade drop bolt.
Best solution would be to braze on mounts for cantilevers. Not so expensive as you think.
Weinmann 900 will reach your guessed at measure. Not common but not at all hard to find. Just do a google search and see all the for sale hits. Cheap too. A good brake that very few want.
Please do not bet your life on a homemade drop bolt.
Best solution would be to braze on mounts for cantilevers. Not so expensive as you think.
08-03-18, 04:52 PM
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To the OP, if you're interested in this route, let me know, I have a few extra pair. They have excellent stopping power. Tektro 559's might work as well.
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08-03-18, 08:23 PM
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As those guys said, Raid or Weinmann 900 could possibly get you there. If not or if you have/find some calipers that are close there are also offset pad holders with built-in drop. BDop is the first hit I found and they offer ~7 mm additional reach. I don't have experience with them, but something to consider. Others here have used them. Then again, what size 700c tire will fit vs 650b - that's a good point above.
Agreed that the first step is to get real world reach measurements front and rear. Slip in wheels that you have and get the pads adjusted to the rim, then account for the difference in brake track / rim radius with respect to existing brake reach. See where you're at.
My first 650b conversion was the Windsor Carrera Sport below. It was designed for 27" wheels, so not necessarily a candidate to search out - but I had the frameset and some parts... That bike wound up first with Weinmann 800 and 900 calipers front and rear, respectively, then a 750 in front after swapping in a low trail 700c replacement fork after the first junky 27" replacement (stock fork had significant rust at the joint to one of the fork ends...). Kool Stop pads and holders. The braking feel was not excellent, but it certainly worked well enough. I could lock or lift the rear, but it was just a bit mushy getting there. Raids might be better in that regard. It was plenty for me to enjoy and after a year+ decide to get a more purpose-built 650b rig with canti's and plenty more goodies (thanks to gugie!).
Go for the experiment. If measurements or whatever don't pan out you could get plenty of 700c rubber in there.
Weinmann 900:
(I also filed the slots a bit to get the pads located on the rim comfortably)
27" wheel bike w/ 650b:
https://www.bikeman.com/bikeman-blogs...sion-guidlines is a good primer.
Agreed that the first step is to get real world reach measurements front and rear. Slip in wheels that you have and get the pads adjusted to the rim, then account for the difference in brake track / rim radius with respect to existing brake reach. See where you're at.
My first 650b conversion was the Windsor Carrera Sport below. It was designed for 27" wheels, so not necessarily a candidate to search out - but I had the frameset and some parts... That bike wound up first with Weinmann 800 and 900 calipers front and rear, respectively, then a 750 in front after swapping in a low trail 700c replacement fork after the first junky 27" replacement (stock fork had significant rust at the joint to one of the fork ends...). Kool Stop pads and holders. The braking feel was not excellent, but it certainly worked well enough. I could lock or lift the rear, but it was just a bit mushy getting there. Raids might be better in that regard. It was plenty for me to enjoy and after a year+ decide to get a more purpose-built 650b rig with canti's and plenty more goodies (thanks to gugie!).
Go for the experiment. If measurements or whatever don't pan out you could get plenty of 700c rubber in there.
Weinmann 900:
(I also filed the slots a bit to get the pads located on the rim comfortably)
27" wheel bike w/ 650b:
https://www.bikeman.com/bikeman-blogs...sion-guidlines is a good primer.
Last edited by Sir_Name; 08-03-18 at 09:09 PM.
08-04-18, 07:43 AM
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Ok I measured the current set up with 700c wheels. I’m almost positive it originally had the 27”. The front brake is currently at 75mm and the back at 80mm. So an additional 19mm would be 94mm front and 99mm in back.
Would the weinmann 900 work for this?
Thanks everyone!
Would the weinmann 900 work for this?
Thanks everyone!
08-04-18, 11:04 AM
#11
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Yes, the 900 will work with that reach. It is a good brake. It will stop you safely without fuss in most conditions. But be realistic. If heavily laden, on extreme grades, at speed a brake arm that long has limitations. Ordinary citybike service the old 900 is all you need. If you plan to use the bike hard cantis are a better idea.
Weinmann is an old standby that does not get sufficient respect. I've just never heard of anyone having trouble with them. My '50 Bates has '59 Weinmann 750 at max reach and those do get used hard. And perform very well. If Weinmann had stopped after 50,000 units their brakes would be ultra collectible legends. Instead they made millions of near perfect brakes and everyone ignores them.
Weinmann is an old standby that does not get sufficient respect. I've just never heard of anyone having trouble with them. My '50 Bates has '59 Weinmann 750 at max reach and those do get used hard. And perform very well. If Weinmann had stopped after 50,000 units their brakes would be ultra collectible legends. Instead they made millions of near perfect brakes and everyone ignores them.
