Which titanium frame?

[pwa]

I think the message is, if having the 57mm brakes maxed out (for clearance) is the objective, do some checks to find out what you will be getting. The Sabbath examples in Bruceys pics look suspiciously like Spa in that regard. Which means 28mm tyres will go in but will easily get clogged with grit and mud. But things change and maybe Sabbath have corrected that. Thorn (steel, I know) boast that their latest Audax frames now have maxed out brakes, having decided that their manufacturer can work to close tolerances. Maybe Sabbath have followed the same path, but I'd check. Ideally I'd see one, built up, before ordering.

My own Spa is fine with 25mm tyres, which is the size I was leaning towards before buying it. I have used 28 and 25 and I don't have a clear favourite. I climb easier on 25 but 28 offers a tiny bit more smoothness on chip and seal.

[NetworkMan]

I think the message is, if having the 57mm brakes maxed out (for clearance) is the objective, do some checks to find out what you will be getting. The Sabbath examples in Bruceys pics look suspiciously like Spa in that regard. Which means 28mm tyres will go in but will easily get clogged with grit and mud. But things change and maybe Sabbath have corrected that. Thorn (steel, I know) boast that their latest Audax frames now have maxed out brakes, having decided that their manufacturer can work to close tolerances. Maybe Sabbath have followed the same path, but I'd check. Ideally I'd see one, built up, before ordering.

My own Spa is fine with 25mm tyres, which is the size I was leaning towards before buying it. I have used 28 and 25 and I don't have a clear favourite. I climb easier on 25 but 28 offers a tiny bit more smoothness on chip and seal.

I remember reading that about the Thorn however I've got the Thorn Mk3R 2018 brochure and on the front page there is a picture of a blue bike. If I zoom in to see the rear brake I'm pretty sure I can see the shiny wheel rim through the gap at the bottom of the brake slot, so not at the bottom of the slot. Pictures from their "Mega Brochure" do show the blocks at or near the bottom of the slots. Thorn say they have recently raised the rear brake bridge by 1.5 mm because they are more confident about tolerances (now +-0.5, mm previously +-2 mm - not clear to me just what that means). It's confusing - they say the danger is that you risk hitting the tyre while surely the danger would be that you couldn't get the block low enough and risked running off the rim at the top.

Actually I'm confused by just what a 57 mm drop brake buys you. Is it the distance between the mounting and the middle of the slot? Do some models have longer slots than others? Do some models have thicker arms up near the mounting bolt? How much is a picture of the brake block in the slot telling us about the clearance under the brake arms or bridge.

[amediasatex]

Thorn say they have recently raised the rear brake bridge by 1.5 mm because they are more confident about tolerances (now +-0.5, mm previously +-2 mm - not clear to me just what that means)

That means that previously the manufacturing tolerances their famebuilder would work to was +/-2mm, so if they specified 55mm drop then frames could arrive with *actual* drop of between 53mm and 57mm depending on where the builder on the day put the bridge. So they bascically had to specify some leeway and ask for 55mm to make sure every frame arrived and was actually able to use a 57mm drop brake.

Now they reckon their builders can work to +/-0.5mm so they can now safely specify 56.5mm and frames will arrive between 56mm and 57mm, much better

It's confusing - they say the danger is that you risk hitting the tyre while surely the danger would be that you couldn't get the block low enough and risked running off the rim at the top.

If the drop is too big for the brakes then the blocks run off the top of the rim then they hit the tyre.

Actually I'm confused by just what a 57 mm drop brake buys you. Is it the distance between the mounting and the middle of the slot? Do some models have longer slots than others? Do some models have thicker arms up near the mounting bolt? How much is a picture of the brake block in the slot telling us about the clearance under the brake arms or bridge.

As far as brakes are concerned, the maximum drop is the distance from the middle of the mounting bolt, to the middle of the pad when the pad is at the lowest point in the slot. So if a brake is advertised as 47-57mm drop that means with the pads at the top of the slot it is 47mm from bolt to pad, when the pads are at the bottom of the slot it's 57mm from bolt to pad, and you're free to adjust the pad anywhere in between. There is of course sometimes some leeway here too and you might be able to squeeze 57.5 or 58mm out of some brakes, or more with a little filing of the slot.

Some brakes have longer slots but no more overall reach, ie: made up example here, they might be 43-57mm reach, so the slot i' s a few mm longer but still can't drop the pads any lower than 57mm. Brake pads can also play a part here as they can vary in height by a mm or so as well, so use tall/thick pads and you might rob yourself of some clearance and have pad to tyre contact when at the extremes of brake reach.

As far as frames are concerned the drop is from the centre of the brake bridge (where the brake bolt goes) to a point that represents the middle of the brake track of the rim. This is the crux of the matter, in that rims differ, not by much, but they do differ. You can work to a standardised dimension, or to two different particular rims, and you might get three different measurements, hence on off-the-peg frames there's always some leeway, there has to be, and why often in the real world tyre clearance/brake drop varies from frame to frame and build to build.

If you got to a custom builder and specify your intentions with respect to clearance they will often ask you what exact rims and brakes you're going to use, and some will even ask to have the wheels and brakes off you to measure and test fit with, or if they are also building your wheels they'll build them first to make sure they squeeze every last mm of clearance out of your chosen components.

[NetworkMan]

Thanks for the very thorough reply. I can see more clearly now....
I'd forgotten that 57 mm is shorthand for 47-57 mm drop and my ancient addled brain had somehow transposed tyre and rim (strange wheel!) so I'd visualised the tyre coming off the rim rather than hitting the tyre. No, I don't know how I did that either.
SO... Presumably the frame maker is working to a spec which puts the brake bridge at some distance 622+X mm from the dropouts +- whatever tolerance they are working to.
X must depend on the distance of the brake track centre to the rim seat, the desired brake drop and a small correction since the brake calliper is to one side of the line joining dropout to bridge. I wonder if there is an ERTO standard for the distance of the brake track centre from the rim seat - probably not. All in all a bit of a dogs breakfast.
I'd not like to toddle along to a frame maker with my wheel and pay alot of money for a made to measure frame and find that the rims had just gone obsolete!

[meic]

As the pads wear out, the brake arms come closer together near the pads, which by simple trigonometry makes them effectively shorter.
Brake arms fully maxed out with new pads will probably result in slashed sidewalls with worn pads or a buckled wheel, though of course there would not be much clearance to tolerate much of a buckled wheel.

[Brucey]

the brake track extends to the rim OD and the lips on the rim are a fixed height above the tyre seat, so whilst some brake tracks are deeper than others you don't need to set the brake blocks low with them.

Building frames super-accurately is difficult because brakes very slightly in how far they stand off the frame, and a tiny change in the angle of the drilling through the brake bridge can make a small difference to the effective brake drop too. Rim width can affect things slightly also. If you have a frame custom built, and want the brake blocks to be in the bottom of the slots, often the builder will ask you to supply the brakes you intend to use, so that the fit can be checked before the bridge is brazed in position.

BTW in SP brakes the reach increases as the brake blocks wear, unless the brake blocks have a tapered cross section. With DP brakes one brake block goes downwards and one goes upwards as the brake blocks wear. The latter can easily go into the tyre. It happens often.

cheers

[freeflow]

My custom Burls was specified for 40c tyres with mudguards. It is designed for disc brakes but I also had Canti bosses fitted for the rear wheel.

[NetworkMan]

Just to return to the thread title since someone may want the information. I emailed Sabbath earlier this month to ask about the front centres on the medium (54) and large (56) frames since the top tubes looked a little short. The replay came from Spa (they bought Sabbath)! 593.4 mm for the medium and 604.1 mm for the large. For me (size 8 or Shimano 43) that meant toe overlap in the 54 and that the 56 might be close. Spa said that the September is a little more "sporty and racy" than their own bike.

[The utility cyclist]

Update:
So i bought a 2nd user Sabbath September after a deal fell through for a one off double butted variant. I've managed to fit a 31mm (measured) tyre under a 35mm guard on the rear, they're actually 28mm Panaracer Race Evo's but are coming up bigger on my H+Son TB14 rims. I could just use the Schwalbe Ultremo 25s which will likely come up nearer 28 which was the requirement originally but i thought why not try bigger. The silly thing is if Sabbath had moved the brake bridge a little higher they'd be room for something like a 39mm guard under a std drop brake and make the clearance better.

The brake pads are not even halfway down the slot, wondering if I could fit a pair of the newer Ultegra short drop calipers which have improved clearance over the previous design and see if I could get the guard under that as an experiment.

The bike came with the original Deda 'Blackrain' carbon forks, they'll only just get the 35mm guards between the blades, I've fully inflated a 28mm giant tyre which on a different rim is spot on 28mm but it'll only just get under the guard. I've looked at the carbon forks on a Roux menthe and there's far more scope for a wider guard, oh well can't have everything and it's not so bad with it being the front tyre.
Been able to get a measured 30/31under the guard at the rear is a real bonus, just somewhat annoying that manufacturers won't design bikes to take wider tyres and guards unless you go disc or V/cantis.
Was reading that the latest Specialized Roubaix has lost its mudguard eyelets and folk are now not buying that model specifically because of that. Really is the tail wagging the dog in terms of provision for practical cycling/bicyclists

[NetworkMan]

Are you measuring distance from bead seat to tread or width?

On the Spa Ti I measured the distance between the RX100 brake bridge and my 25 mm Schwalbe One Evo which measures about 25 mm width. That was 12 mm so I estimated that allowing 2 mm for a guard that would allow 7mm clearance with a 28 mm tyre. How much clearance do you reckon you have on the September with your 28 mm tyre? BTW the brake is about mid-slot at the back, towards the top at the front, so I reckon probably only a decent clearance for a 25 mm tyre here.

[Freddie]

Looking at this thread, it seems a lot of energy is put into trying to figure out how to fit a reasonable size tyre and mudguards onto bikes that are not quite racing bikes, but not quite as functional as they could be either.

Why not just increase the 47-57mm standard to 57-67mm - most people are using larger tyres these days, does an extra 10mm under the fork crown really slow anyone, when they are using mudguards already. What would be the objection to this?

[The utility cyclist]

Looking at this thread, it seems a lot of energy is put into trying to figure out how to fit a reasonable size tyre and mudguards onto bikes that are not quite racing bikes, but not quite as functional as they could be either.

Why not just increase the 47-57mm standard to 57-67mm - most people are using larger tyres these days, does an extra 10mm under the fork crown really slow anyone, when they are using mudguards already. What would be the objection to this?

Brakes with a longer arm are not as powerful and can be a bit flexy, they look unsightly and for me I don't want a extra wide guard that sits well above the tyre, I like mine as snug as I can get them (i realise this isn't something most want but it is me). 57mm std drop brakes are excellent and more than suffice in terms of clearance, if you must just redesign the brake arch a bit as they have with the newer short drops so they will easily accept 28mm tyres (some report you can get 30mm under there, obvs without guards)

It just takes a little bit of thought by the bike/frame designers* to enable full use of that drop and for the forks to enable that also. The carbon forks on my Roux Menthe take a 35mm guard with ease and when I tried the Panaracer that went in easily enough. So with a std dual pivot you could get 30/31mm tyres AND mudguard, I'm pretty happy with that because I can use the 28s I bought and I'd happily go full loaded touring on 28s, best of all worlds for me.

*There's no development in rim braked bikes/frames, it's all disc now and as I said, tail wagging the dog.

[PH]

*There's no development in rim braked bikes/frames, it's all disc now and as I said, tail wagging the dog.

There's disk brakes frames with no clearance as well, why would they do that?
Glad you've found what you were looking for.

[The utility cyclist]

*There's no development in rim braked bikes/frames, it's all disc now and as I said, tail wagging the dog.

There's disk brakes frames with no clearance as well, why would they do that?
Glad you've found what you were looking for.

I know, just seen a 2019 model Kinesis Scandium disc frame that can only take a 30mm tyre with mudguard and it's touted as a 'bike-packing' bike just why?
As for the bike, it's not perfect, it was well grotty/unserviced but I paid very little for it via ebay, I've stripped it, thoroughly cleaned it and polished all the scratches out and just deciding on a new headset. It's going to have a 3x11 drivetrain and lots of carbon fibre, because I can

[pwa]

On my Spa Ti Audax I put a matt black Hope headset and it really suits titanium. Crisp, neat looks, and all very nicely made. Not cheap.