Is it possible to shorten a bicycle frame?

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pete75
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Re: Is it possible to shorten a bicycle frame?

Post by pete75 »

horizon wrote:Custom build? There are two bike builders who understand the problem and pretty much sort it for me with off-the-peg frames: Spa (thanks to 531colin) and Thorn. But I do want to be sure before splashing out.


Spa have numerous test bikes in most sizes and you can take them out for several hours so a trip to Harrogate might set your mind at rest. Thorn have a return policy if you don't like the machine - can't remember exactly how long but it's more than a week.
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horizon
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Re: Is it possible to shorten a bicycle frame?

Post by horizon »

reohn2 wrote:You didn't give us any (optimum) measurements,sorry to push but without them we have no idea of your ideal.



I'm on the case.
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horizon
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Re: Is it possible to shorten a bicycle frame?

Post by horizon »

pete75 wrote:
horizon wrote:Custom build? There are two bike builders who understand the problem and pretty much sort it for me with off-the-peg frames: Spa (thanks to 531colin) and Thorn. But I do want to be sure before splashing out.


Spa have numerous test bikes in most sizes and you can take them out for several hours so a trip to Harrogate might set your mind at rest. Thorn have a return policy if you don't like the machine - can't remember exactly how long but it's more than a week.


I visited both last year (well worth it, great staff :) ). I do need longer and I'd want to do some adjustments which are a bit outside the remit of a test ride. My plan now is to acquire a second hand bike/frame and give one or other a try out (I've been looking 8) ). Based on what I ride now and the published measurements I'm almost there and I'm happy to risk a second-hand purchase to make a proper assessment.
When the pestilence strikes from the East, go far and breathe the cold air deeply. Ignore the sage, stay not indoors. Ho Ri Zon 12th Century Chinese philosopher
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hondated
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Re: Is it possible to shorten a bicycle frame?

Post by hondated »

Cyril Haearn wrote:If the top tube is shortened the down tube will have to have a double kink
Maybe the couplers justify the price after all if they can get round that :wink:

Still amazes me, given their price, that there still isn't a Chinese equivalent for these couplings.
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horizon
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Re: Is it possible to shorten a bicycle frame?

Post by horizon »

hondated wrote:
Cyril Haearn wrote:If the top tube is shortened the down tube will have to have a double kink
Maybe the couplers justify the price after all if they can get round that :wink:

Still amazes me, given their price, that there still isn't a Chinese equivalent for these couplings.


The couplers don't alter the frame dimensions. What they do do (and therefore justify the expense) is retain the strength of the frame - which is what grabbed my attention.
When the pestilence strikes from the East, go far and breathe the cold air deeply. Ignore the sage, stay not indoors. Ho Ri Zon 12th Century Chinese philosopher
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Gattonero
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Re: Is it possible to shorten a bicycle frame?

Post by Gattonero »

horizon wrote:The recent thread on SandS couplers got me thinking.

Although I have now pretty much nailed the make and type of bike that works best for me (Took you long enough horizon! Ed.) it leaves me with some bikes which I would love to cut in half, take out a cm or two, stick them together again (no need for couplers) and make them shorter.

AFAICS I am talking about the top tube and down tube.

Purely as a matter of interest what stands in the way of doing this, even with replacement forks?


As other people said, not worth because just for the way triangle works, the angles would have to change as well.

My take is, and I know this hurts, if one needs specific measurements then the frame has to follow. I.e. a "shorter" frame may imply a lower flexibility of the body, so one has to think how much a good health is worth. Is not just about using the shortest and tallest stem one can find.
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Audax67
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Re: Is it possible to shorten a bicycle frame?

Post by Audax67 »

Best solution is to grow a bit.
Have we got time for another cuppa?
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Gattonero
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Re: Is it possible to shorten a bicycle frame?

Post by Gattonero »

hondated wrote:
Cyril Haearn wrote:If the top tube is shortened the down tube will have to have a double kink
Maybe the couplers justify the price after all if they can get round that :wink:

Still amazes me, given their price, that there still isn't a Chinese equivalent for these couplings.


Why is normal to consider patent infringement for the sake of saving by the end user? On top of this, it's not just the cost of the part per se, but the fitting as well.
Skilled labour does cost money. Are you ok for people asking a massive discount for the job you do? :roll:
It is by riding a bicycle that you learn the contours of a country best,
since you have to sweat up the hills and coast down them.
Thus you remember them as they actually are...
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horizon
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Re: Is it possible to shorten a bicycle frame?

Post by horizon »

pwa wrote:I know it can cause some people problems if they muck about with their cleats / foot position on the pedals, but if you nudge your cleats back on the shoes by 15mm that has the same effect as reducing the top tube by 15mm in that it brings your upper body 15mm closer to the bars.


Which way do you mean? ATM my cleats are as far as possible back to the HEEL. I find this 100% comfortable and "right". :)

Despite my lamentations about reach, I find everything about my position "comfortable": saddle (Brooks), neck, shoulders, knees, wrists. No aches no pains, all day comfort. I'm getting something right (although it's not for want of trying!). I do feel very lucky about this.
When the pestilence strikes from the East, go far and breathe the cold air deeply. Ignore the sage, stay not indoors. Ho Ri Zon 12th Century Chinese philosopher
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horizon
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Re: Is it possible to shorten a bicycle frame?

Post by horizon »

Gattonero wrote:
My take is, and I know this hurts, if one needs specific measurements then the frame has to follow. I.e. a "shorter" frame may imply a lower flexibility of the body, so one has to think how much a good health is worth. Is not just about using the shortest and tallest stem one can find.


Gattonero: can you say a bit more as I'm not sure I follow. What should one do/not do?
When the pestilence strikes from the East, go far and breathe the cold air deeply. Ignore the sage, stay not indoors. Ho Ri Zon 12th Century Chinese philosopher
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Re: Is it possible to shorten a bicycle frame?

Post by PH »

hondated wrote:Still amazes me, given their price, that there still isn't a Chinese equivalent for these couplings.

Too small a market, if they were selling thousands a week there soon would be.
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531colin
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Re: Is it possible to shorten a bicycle frame?

Post by 531colin »

horizon wrote:..... To accommodate my legs I shift the saddle back - you have to do this or you just sit off the back of the saddle....


This is the bit that worries me.....Generally, you set the saddle HEIGHT for your leg length (with various caveats)
https://www.stevehoggbikefitting.com/bikefit/2011/05/addendum-to-seat-height-how-hard-can-it-be-2/
And setback adjusts the amount of weight on your hands https://www.stevehoggbikefitting.com/bikefit/2011/05/seat-set-back-for-road-bikes/.....scroll down to "point of balance" if you are impatient.
Even if I have my usual saddle setback, I find myself sitting on the back of the saddle if the reach (to the bars) is too short.....I think that's something to do with bracing my back/pelvis against the muscular work of pedalling.
almost the same post here...https://forum.cyclinguk.org/viewtopic.php?f=1&t=120242
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horizon
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Re: Is it possible to shorten a bicycle frame?

Post by horizon »

531colin wrote:
horizon wrote:..... To accommodate my legs I shift the saddle back - you have to do this or you just sit off the back of the saddle....


This is the bit that worries me.....Generally, you set the saddle HEIGHT for your leg length (with various caveats)


Preamble (warning - maybe TLTR!)

I've tried to limit myself at times to talking only about frame proportions. This thread viewtopic.php?f=5&t=118634&hilit=spa+titanium+brushed almost exactly parallels many of the problems I faced in simply understanding how a frame fits together and changes dimensions and angles according to make and size. I'm happy that I can now (almost) buy a bike knowing what it is I am buying in terms of size and fit.

So that's the frame but it leaves all the other variables of body proportion, flexibility and riding style i.e. the rider. It also leaves the possible adjustments - cleats, stem and saddle. As I said upthread, most of "me" is totally happy on a bike but it leaves the niggling problem of reach. This is caused principally by my moving the saddle back further than normal and thus putting the bars out of comfortable reach.

The conclusion I came to is that my overlong legs led me to buy bikes that were generally too large (and coincidentally had usefully long top tubes) but actually not too far wrong for my height. A smaller size would have solved the reach problem (despite the shorter head tube) and that is where I am now heading. I'm going to test one by buying a cheap second hand touring bike in a smaller size and giving it a good trial. I'm also currently using my Dawes Horizon without a VK adaptor to see what that really feels like. It has a 73.5 deg seat angle and I'm thinking that 72 deg might clinch it. I must emphasise though that most of the time I am almost 100% OK - it's just that i cannot really test it out. And I also find that my needs change over the course of a ride - as they do for anyone.


So back to your point: I agree. I had actually come to the same conclusion (it may have been something in this thread). But that leaves me completely in the dark as it might be one of several factors - my leg proportions, upper body flexibility, foot position on the cleats etc. But I reckon you still need to be behind the pedals sufficiently in order to complete the pedal cycle - you cannot bend your knees enough without being able to push you body back. So I still think that seat angle is critical if you have long legs for you height - remember, I am not tall (5'10") but I have long legs for my height (34" inside leg). This, as I see it, throws the balance between saddle height and reach - as you accommodate your legs (by moving your bum backwards, you lose your arm position in relation to the bars. BTW I have plenty of height adjustment on all my bikes. I accept that if I were very flexible that wouldn't be a problem but I like a fairly relaxed upright position - mind you, I still like the bars nearer even when my back drops (bending my arms).
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The longer your thighs the further back your bum must go
The longer your thighs the further back your bum must go
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When the pestilence strikes from the East, go far and breathe the cold air deeply. Ignore the sage, stay not indoors. Ho Ri Zon 12th Century Chinese philosopher
gxaustin
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Re: Is it possible to shorten a bicycle frame?

Post by gxaustin »

I believe a Trek Domaine 4.3 might be worth a look. I tried a friends and it was pretty comfortable. I too have long legs and short body (35" x 5'11").
You can muck about with stems and cleats all you like but nothing beats a well fitting frame in my experience.
Here's an idea: do a frame building course and make your own bespoke frame. I absolutely loved the experience and it was well worth the extra cost for the satisfaction of building it.
Freddie
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Re: Is it possible to shorten a bicycle frame?

Post by Freddie »

Horizon, your problem is that the higher a saddle is at any given angle, the further away it is from the same saddle set exactly the same way vis-à-vis seatpost position (height and fore/aft adjustment) on a steeper or slacker seat tube. Long legs will exacerbate the problem of too steep a seat tube. 73.5 is a steep seat tube. 72 is not (71 used to be quite common back in the 1950s).
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