New frame. Steep seat angle. Unrideable.

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JohnW
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Re: New frame. Steep seat angle. Unrideable.

Postby JohnW » 11 May 2019, 11:50pm

Can I offer a word of comfort for the OP?

It wasn’t until this current thread came onto the Forum that I realised this : mentioning no names and not wanting to give identities away, but reading between the lines, I recall that about15 years ago I had the same issue with a frame by possibly the same framebuilder. I was measured for this frame, and believed that all would be perfect. I was told that the seat angle would be 74º. I already had two 73º and one 74º frames and this seemed natural. I don’t buy bikes – ever since I was a teenager (going back to the 60s!) I’ve built my own bikes up around frames and I just built a bike around this new frame. I have quite a stock of components, and I have always built up using used tackle until I got the bike right, and than bought new as necessary.

Also, being aware that no two frames are identical and no matter how we try, we’ll never get two bikes to be/feel identical, I wasn’t phased when it took me some time to get the saddle right. In fact, none of my saddles seemed to be right, even with a new lay-back seat-pin (Velo-Orange Gran Cruz) it still wasn’t right. But for me, at the time, this was no big deal – it was just how it is when building a new bike. It seemed that my sit bone position in relation to the pedal spindle wasn’t right. I couldn’t get any of my Brooks saddles back far enough. The bike was alright – rode well and handled well – but not just that bit extra that I was used to. I had another saddle (I think it was an old suede-covered padded Milremo, with moulded plastic core) – and that was fine. The bike now rode like a dream and I forgot all about the issue. I’ve since bought a Spa leather saddle, which is a bit hard yet! – but gets the right position.

This afternoon, and stimulated by this thread, for the first time I measured the seat angle on this frame, and lo-and-behold it comes out at a little over 76º! I’d had and solved this issue years ago!

It had never occurred to me to check the seat angle – I just sorted it as we do. The bike rides perfectly well and the stem gives the same handlebar position in relation to sit-bone position on the saddle as on my other bikes.

There’s a solution to the OP’s problem.

What would concern me a bit is that the OP has had to have the forks replaced due to manufacturing error, and the frame-builder’s excuse of avoiding toe overlap is invalid, because toe-overlap exists. I think I’d be unhappy about that. I think that the frame-builder has some questions to answer there.

Despite my bike as it now rides, I still think that 76º is not a suitable seat angle for a frame that is going to be used for general road-riding – personally I think of that as pure waffle.

Thank you to Brucey and Colin 531 for your input – that was good stuff – we should all inwardly digest it. Incidentally, consulting the Spa frames information (on their web-site) I find that their seat angle for Audax bikes is 72.5º, which is my opinion is much more appropriate than 76º

srb88 wrote:..................The frame is an 'off the peg', 'audax' model, 21 inch, in their 'standard' geometry....................on the first couple of rides, found that the saddle felt too far forward.........................I contacted the maker, to ask what was going on, and was told that this is correct - that is the intended seat tube angle for that model...................They explained that this is done to avoid toe overlap and is 'common practice'. I found this extraordinary......................The best bit is - I still have toe overlap!
...............NB: The fork I'm using is the appropriate length - very close to the specs of the original fork, which I had to send back for modification as the brake pads sat too high on the at the bottom of the slots - nearly touching the tyre. The company was happy to sort this, though claimed at first it seemed fine to them. (It definitely wasn't)......................

PH
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Re: New frame. Steep seat angle. Unrideable.

Postby PH » 11 May 2019, 11:55pm

srb88 wrote:
PH wrote:That sounds ideal, maybe something Cycling UK could consider, some form of independent technical expert who could be called upon to to advise and report. Such an officer would be of great benefit to cycling in general as well as the membership :twisted:


That isn't a bad idea at all. It would be a way of formalising the expertise on forums such as this one to encourage companies to take it seriously.

Apologies, there's a backstory and I shouldn't have made the assumption that everyone knew it
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Jezrant
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Re: New frame. Steep seat angle. Unrideable.

Postby Jezrant » 11 May 2019, 11:59pm

Crikey, what a saga.

BTW, for anyone thinking of boldly going forth to buy a small (or very large) frame, I'd highly recommend a read of Tony Oliver's still very valuable book.

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NATURAL ANKLING
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Re: New frame. Steep seat angle. Unrideable.

Postby NATURAL ANKLING » 12 May 2019, 2:30am

Hi,
I just started riding my road bike which is a 1983 Koga-Miyata 60cm (its actually 23", centre to top 578mm, don't ask) I will check tomorrow but I have it down as 75 degrees on the seat tube. TT about 570mm.
IIRC its about 72 head tube.
The saddle a rather cheap selle mach 1 in almost all the way back. with 57-60mm layback.
(Front of saddle to hoods is same as my tourer which has a 575 top tube, ST centre to top 600, IIRC 72 both angles.
Saddle is all the way forward tourer :P)
I used to ride it successfully no problem about 25 years ago.
Theres always toe overlap on those things, but I will have to check tomorrow, it might clear, on the turbo at the mo.
Not sure about steering specs.
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brynpoeth
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Re: New frame. Steep seat angle. Unrideable.

Postby brynpoeth » 12 May 2019, 6:35am

Up to now I thought Traditional Frames were just wonderful, this story has opened my eyes
I sometimes take goods back for a refund, usually no problem, but guarantees are very problematic for example for an air-Con system that does not work, costs an awful lot, the installer might claim that it works. Cannae take one back to the shop or fix it oneself
What a con
..
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Brucey
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Re: New frame. Steep seat angle. Unrideable.

Postby Brucey » 12 May 2019, 9:11am

FWIW it is incredibly difficult to measure seat angles exactly, and anyway if there is another error, e.g. fork length isn't quite right (eg if the lower part of the headset is a different height) then the top tube won't be horizontal (or at the intended angle) regardless. This means that you can (with difficulty) measure the seat tube angle to the nth degree and it is still 'wrong' from a riding position POV anyway.

The good news is that you don't need to measure the seat tube angle (knowing it just gets you in the right ballpark); you just need to get the saddle and the handlebars in the right place, which is not quite the same thing (it depends on the saddle and seat pin being used). If you look at most of my bikes you will find a small mark on the top tube; this is a 'top tube sighting mark' (TTSM) and allows you to get the saddle and handlebars in the right place without measuring any tricky angles, even if the whole bike isn't sitting at the correct angle for some reason.

The method is to choose a flat surface and to drop a plumb line to the exact centre of the BB. Mark the top tube where the line intersects it. Now turn the bike 180 degrees so that the tyres sit in the exact same positions on the floor/ground and repeat. If the ground/floor was perfectly flat the two marks will coincide; if not, take an average. This is your TTSM. (Marker pen will last long enough to get set up but if you think you might tinker in the future, some kind of more permanent mark isn't a bad idea.)

Now you can offer up a ruler to the saddle nose (or cantle plate with a leather saddle) and sight three points (like a gunsight) being 1) the BB centre, 2) the TTSM, and 3) the scale on the ruler. You can set the saddle setback (for any one brand of saddle) to within ~2mm quite easily. Then set the reach from the saddle to the handlebars. Double-check that the saddle height hasn't been changed by a large fore-aft adjsutment, and if it has, adjust the saddle setback again to suit.

This method allows you to transfer a riding position from one bike to another with a high degree of accuracy, even if you don't know the angle of the seat tube on either frame.

FWIW the seat angle and the type of seat pin/saddle you use all make a substantial difference; IME if you intend to use a brooks leather saddle this has (vs some other saddles) a similar effect on the range of saddle adjustment as about two degrees increase in seat tube angle, or a (real) 20mm change in seat pin layback; once you realise this, the typically slack seat angles of yesteryear make a lot more sense....

cheers
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srb88
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Re: New frame. Steep seat angle. Unrideable.

Postby srb88 » 12 May 2019, 11:06am

Brucey wrote:FWIW it is incredibly difficult to measure seat angles exactly, and anyway if there is another error, e.g. fork length isn't quite right (eg if the lower part of the headset is a different height) then the top tube won't be horizontal (or at the intended angle) regardless. This means that you can (with difficulty) measure the seat tube angle to the nth degree and it is still 'wrong' from a riding position POV anyway.

The good news is that you don't need to measure the seat tube angle (knowing it just gets you in the right ballpark); you just need to get the saddle and the handlebars in the right place, which is not quite the same thing (it depends on the saddle and seat pin being used).


Quite agree, though in this case 2 methods gave similar results (actually came to over 76 degrees), and both relied on ensuring the top tube
(which is supposed to be horizontal) was horizontal using a spirit level first, so it was parallel to the floor and then going from that. I also checked on bike geometry calculators that with a bike of this dimensions, what effect a change in fork length would have, providing the same offset. Even a 10mm difference in fork length only resulted in a 0.5 degree change in seat tube and head tube angles, so any appropriate fork would deviate less than this - likely 3-5mm in axle-crown length.

I've done same on my rigid 29er mountain bike, when using a shorter fork to experiment with sharper handling and a lower bar position. The bike is designed for a 100mm suspension fork, so a 470-475mm rigid fork is appropriate. Had a 470mm one on. I tried a 450mm fork with similar offset and it steepened things up a bit too much, though did feel good on climbs.

srb88
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Re: New frame. Steep seat angle. Unrideable.

Postby srb88 » 12 May 2019, 11:16am

Brucey wrote:FWIW the seat angle and the type of seat pin/saddle you use all make a substantial difference; IME if you intend to use a brooks leather saddle this has (vs some other saddles) a similar effect on the range of saddle adjustment as about two degrees increase in seat tube angle, or a (real) 20mm change in seat pin layback; once you realise this, the typically slack seat angles of yesteryear make a lot more sense....

cheers


Indeed - so if I'd used a Brooks on the frame in question - which I considered for long ride comfort - I'd have been looking at around 22-25 mm setback. Possibly this can be masked on a well used Brooks due to the hammock effect reducing the feeling of falling off the front of the saddle, but I think you should be attaining balance through an appropriate position, not relying on a saddle to cup your groin...

Brucey
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Re: New frame. Steep seat angle. Unrideable.

Postby Brucey » 12 May 2019, 3:20pm

FWIW floors are not always perfectly horizontal, hence my suggestion of turning the bike round when you are using a plumbline on it, and checking the reading comes out the same, and/or averaging it.

I'm sure that not everyone sits on (or in) a Brooks leather saddle in the same way but most people sit further forward on one of these than a plastic hulled saddle. Furthermore the parallel section of the rails doesn't extend a long way forwards. I guess each thing is potentially 'worth' about 10mm. IIRC Spa leather saddles have a slightly longer parallel rail section so they will adjust further rearwards and in addition ( esp when they are new) they are pretty hard, so maybe you can sit further back on them too.

cheers
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531colin
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Re: New frame. Steep seat angle. Unrideable.

Postby 531colin » 12 May 2019, 6:54pm

srb88 wrote:Re the above suggestion for an appointed technical advisor - doesn't Richard Hallet build frames and write for Cycling UK? …….....

Yes, he is in the bike trade http://www.halletthandbuiltcycles.com/ and also the technical editor of CUK's magazine. How is that not a conflict of interest?
Surely in the case of a dispute between a customer and for example a framebuilder, anybody giving a professional opinion on the suitability of the goods must be seen to be completely independent and impartial.
In the real world, the whole idea falls down because a sensible fee for the services of a suitable individual is out of proportion to the sums of money involved in such a dispute.

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531colin
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Re: New frame. Steep seat angle. Unrideable.

Postby 531colin » 14 May 2019, 6:40pm

Jezrant wrote:…….BTW, for anyone thinking of boldly going forth to buy a small (or very large) frame, I'd highly recommend a read of Tony Oliver's still very valuable book.

Skip his bit on steering geometry, its much better explained in Wikipedia.....https://en.wikipedia.org/wiki/Bicycle_and_motorcycle_geometry
Jobst Brandt had something to say about shimmy in big frames, while looking for it I found this, which at first glance looks useful....http://www.thetallcyclist.com/2016/09/custom-bicycle-framebuilding-geometry/. Didn't find Brandt's stuff......

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531colin
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Re: New frame. Steep seat angle. Unrideable.

Postby 531colin » 14 May 2019, 6:55pm

I have a bricklayer's four foot level, and a plumb-line. Its pretty easy to stand one wheel on a bit of packing so the bike is level. To get my saddle setback I just drop the plumb-line from the saddle and measure where it comes relative to the bottom bracket axle. Different shape saddles will require a different setback, so it isn't all plain sailing. I'm not too sensitive to setback, plus or minus 5mm doesn't seem to matter; I like to move about on the saddle anyway. (Saddle height is more of a difficulty; I can't stop myself adjusting the height less than 5mm for shoes of different sole thickness....just another obsession :roll: )
I suspect more people have a smartphone than a long level, and I know that apps are available to measure angle of inclination (to the horizontal?)
Anybody done this? It could be useful to get a quick idea of seat tube angle? I guess you could use the phone to check the floor is level as well?

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cycleruk
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Re: New frame. Steep seat angle. Unrideable.

Postby cycleruk » 14 May 2019, 8:01pm

Seat tube angle - Would a straight edge (or string) across the wheel hub centres + a protractor be O.K for measuring the seat tube angle?
Wouldn't matter then about top tube or floor levels. :?:
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fastpedaller
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Re: New frame. Steep seat angle. Unrideable.

Postby fastpedaller » 14 May 2019, 9:00pm

cycleruk wrote:Seat tube angle - Would a straight edge (or string) across the wheel hub centres + a protractor be O.K for measuring the seat tube angle?
Wouldn't matter then about top tube or floor levels. :?:


I should think so - I used a 'digital angle finder' from Lidl to similar effect to measure the seat tube angle on my Rudge Montague folder. Just by eye from several feet back should suffice, with a straight edge held on the base of the protractor and sighted on the wheel centres (if that makes sense)

Brucey
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Re: New frame. Steep seat angle. Unrideable.

Postby Brucey » 14 May 2019, 9:11pm

the plumbline technique described previously is very simple, very accurate, and pretty foolproof.

By contrast when measuring angles directly it is easy to get a ~1 degree error, and this would (in an average sized bike) correspond with an error in the plumbline measurement of about 10mm; a huge error.

cheers
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