toppcatt

Hi
I am currently riding an old Brompton (about 10 years old I think). I cycle 2 miles to the station, then 5 miles across London each day, each way and have been doing so for the last 5 years. Over the last year I have been getting knee problems for which I have been having physiotherapy for the last 9 months with only limited results and now facing a trip to see a consultant surgeon. The knee problems started when I started upping my road bike and mtb mileage, but has been lurking for many years (I don't run any more either). One of the things that I have noticed over the last year is that my knee gets sore when I get on the Brompton after having done some longer (35-85) mile rides over the weekend, or recently I managed 8 pain free days over xmas (160 miles in 8 riding days out of 12, av 30 miles a trip) only to get on the Brompton and get a pain in 10 mins. It appears that the Brompton is often the straw that breaks the camels back, one factor in the equation to be eliminated.

I can't help feeling that the riding position is to blame. I ride my other bikes well set up (e.g. according to Andy Pruitts book) and the Brompton with as long a seat as I can get and seat as far back as I can, but I still feel upright.

Looking at the new S-Types I wonder if this position would help change my geometry on the bike enough sort things out. I have heard that the more recent Bromptons are longer than my 10 year old is that true? Or do I need something more stretched out?

I am looking for any opinions or suggestions. I am open to the idea of buying a new bike or modifying my existing one. I am not tied to the Brompton, but the compact fold is very important for the train leg of my journey. I have not got around to test riding an s-type yet or anytyhing else, but it is on my list of things to do when I can get over to a shop with them in.

TIA

badmother

Are you sure the gears are right for you? Are you spinning fast enough or struggeling and pushing hard and slow? What sort of bars on it now?

makingmark

you said "any opinions"--here is one you might not get from other forum members:

are there any stressors in your life right now, aside from the physical pains you mention?

problems with job, family, sense of self esteem?

the mind is powerful, and it tries to protect us. sometimes, it will displace some feeling we aren't willing to face somewhere else.

i say this from personal experience. there have been times in my life that i got the itch to buy something i didn't really need. things would line up to make it seem that i really needed that thing. i would make the purchase, and things would be good for a while - but then something else would pop up.

i also had a relative with a job that required use of his hands. he developed carpal tunnel. did acupuncture, physical therapy, meditation - it turned out that he was having a lot of trouble adjusting to a new boss, and love problems. once he became aware of that, the carpal tunnel disappeared.

i hope you won't be offended by what i say, and if you are, i apologize. this may not be your situation. but it could be, which is why i offer it in all good intention.

toppcatt

The gears are the 3 speed AW hub with the 54 tooth chain ring (+8%). I guess this could be too high, but it makes the middle gear more usable, I do try to not use the high gear all the time and make sure that I am spinning (as I would on my mtb or road bike). This was one of the thoughs about a new bike, the chance to get more gears, may help with getting a better gear. With only three gears, they are quite well spaced apart, often neither the high or lower fits your terrain/wind speed and you seek an inbetween gear. Would a 6 speed Brompton give me the fill in gears or just more higher and lowerr than my current range?

The bars are the old original style M type, which makes the riding position quite upright, hence my thoughts about an S-type.

On makingmarks suggestions, I am not offended and is a good suggestion however I think this is a genuine problem, I have had a history of knee problems, in the past brought on by running or hiking with heavy loads. I am content in work and home life so I think that I can rule this out.

jur

I am thinking along the lines of different Q factor for the Brommie. Are you using clipless pedals?

EvilV

Maybe your seat height is an issue. Try varying the position of your foot on the pedal - changing the contact point from instep to toe. This effectively allows experiment equivalent to quite a large extension of the seat post which you can try on the fly without adjustment.

I have occasional trouble with my left knee and find that I can get relief by this method. It seems a lot less painful (when it happens) if I push the pedal with my toe rather than the ball of the foot or instep. This trouble always starts for me when I have been hill climbing in too high a gear.

The last point brings me to this question: Is your Brompton over geared for you? You mention your mountain bike not giving you the problem. Maybe that is because it runs lower gears, or you have the option of them when the knee starts to give trouble. You can lower the gear ratio of the Brompton by getting a smaller front chain wheel. Pushing too high gears puts a lot of strain on the knee, especially if the seat height is too low.

PDR

If your current Brompton is 10 years old it will have the shorter frame. Later frames are an inch longer.
I have a B-Spoke S-Type on order. I tried M-type bars but preferred the S-Type, which are 2” lower and further forward.
You could try something like what Little Pixel has done here:

https://www.bikeforums.net/showthread...&highlight=vro

https://www.bikeforums.net/showthread...=364890&page=3

jagatron

Where are your knees relative to the pedal axle for the Brompton vs. the other bikes?

Q factor like Jur says is something that gets me between bikes, too. Distance between the two inner pedal edges between the different bikes?

toppcatt

I am not aware of Q factors, I shall have to look this up. I am not using clipless pedals on the Brompton, just trail shoes and standard Brompton pedals. On my other bikes I use Time ATACs.

toppcatt

One think I notice when I look down at my feet is how far forward the BB is and hence the pedals relative to say my road bike. This is partly because I have the saddle as far back as it will go (seat clip to rear, far back on the rails) and partly the Brompton design with a long angled seat tube.

My shoes are a bit chunky trail walking shoes, and with the possibility of heel stike on the coaster wheels, it may be that I am putting my feet wider apart than I should. Perhaps riding clipless would help improve things here, certainly worth a try if I can get the pedals off (RHS was stuck firm last time I tried!).

folder fanatic

There are many things you can do to improve any model from any year of the Brompton bike. I should know as I have done so successfully with my own Brompton C3 by adding a new saddle (minus the Saddle Adapter Pin with Quick Release-I did not need it), rotating the brake levers upward very slightly to reach my fingers for improve comfort and braking leverage. and even decent Kool Stop Brake pads. All of my upgrades were far less than I expect to pay at less than 100 US dollars. I recommend that you visit your own Brompton dealer as well as other bike retail sources to see what is offered to you. Personally I think that the part: Saddle Adapter Pin with Quick Release is what you need. Over here in the US, C.M.Wasson Co. offers the part. I like the ability to fine tune your height as well as pedaling position with ease as seen with his own photos. You also gain the ability to remove the saddle without tools when you store the bike or travel with it.

Visit his link for more information on this and other parts and accessories: https://www.foldabikes.com/PriceListHTML/npricelist.php

toppcatt

I like the idea of the Saddle Adapter Pin. How does it affect the ride, it would put you quite far back over the back wheel, further from the BB. I already find myself pulling wheelies, this looks like it will increase the chance of that, could be fun! Some of the material on bike setup I have read suggest you only want to be far enough back so that your knee is in line with the pedal spindle when pedals are horizontal. Being this far back with a SAP may cause problems, I shall have to watch how it goes.

I was going to ask if anybody knew where to fnd them in the UK, but a quick Google came up with a number of stores selling them so, as a first effort for £12 it is worth a go on the existing M-Type.

I still feel inclined towards buying a new S-Type and then applying some of the great suggetsions from this thread, but may try some while I await a new bike. Any other ideas welcome. Go to visit the Consultant Orthopaedic surgeon tomorrow, so it will be interesting to see what he has to say.

EvilV

How tall are you? Or maybe I should be asking what your inside leg measurement is. Perhaps your seat post is too short if you are having to sit far back. I know you have been riding the bike for some years, but a small injury acquired recently could be made worse by not having the right amount of leg extension.

jur

Instead of going to a surgeon, perhaps you should see someone who's an expert on bike fit and related injuries.

I get slight knee twinges (inside the joint, not the tendons) when riding the Mini for a while. I'm pretty much convinced it's Q factor.

But in your case since you don't use feet position thingies on the Brommie it could be a few foot position issues. I would try it out with some clipless pedals just at least to see the effect. Foot position is really important.

toppcatt

Well I am 5'10" and have an inside leg of 31 inches, but I already have the extended seat post with a rail saddle, but don't extend it fully as it is too tall that way. I do like a well extended saddle (but not not over extended) and like to keep my legs well extended. I had the physio look at me cycling this bike and she was reasonably satisfied that my position was right and has quizzed me about my other bikes and how I am set up.

toppcatt

The Surgeon visit is the natural end to the physio treatment and is being paid for by health insurance. The physio believes she has done all she can to stretch things and strengthen all the right muscles to improve leg position. They then refer me to the consultant who may do an MRI scan to help his diagnosis. In the long run I do need to reduce the the factors that aggravate the injury (bike, body, habits) but may need to have stuff repaired if there is damage.
We did talk about foot position and their standard treatment is to support the heel (e.g. for runners with a similar problem), but this is no good for a cyclist where it is all about the ball of the foot at the contact area. I will definitely try out the clipless pedals next.

badmother

Sure your seat is comfortable? Not resting some of the weight on feet and some on the hands that should have been on the seat? Or discomfort in hands leading to not resting properly on the bars, leading to more weight on (uncomfy) saddle and feet? Just thinking. Did you try "bar cones" on present bars just to get an idea of more stretched out?

cyclistjohn

For the past several weeks, I've been riding almost daily, a M3L fitted with 155 mm cranks. Recumbent riders particularly favour shorter cranks as it apparently alleviates knee problems for them. I do ride a recumbent in summer, but as yet, haven't fitted shorter cranks to it, as mine are 130 BCD, suitable for big chain rings like a Brompton generally uses, but my recumbent needs 110.

I've had no knee problems so far (~ 500 miles), & they're better for going around bends at a decent speed, since I no longer get pedal strike. I fitted a 46t chainring, as that's all I have, & the existing 50 t Brompton ring is swaged to the crank arm, so I couldn't use that.

My inside leg is 30", & I have the standard tube but now with the (standard PU) seat at the absolute top of the tube, to compensate for the 15 mm shorter cranks.

If you get or borrow a set, it might be worth trying?

HTH,
john

LittlePixel

I thought the Brompton came with the saddle adaptor pin as standard as a measure to tuck the saddle forwards and achieve a more compact fold...

toppcatt

The idea of using shorter cranks is one that I never considered before, I took it as a fixed attribute like frame length. I suppose there is the trouble of finding a suitable chainring with suitable length crank, but definitley worth an investigation. The BB is just standard square taper so should not be too difficult I guess.

Hopefully my saddle adapter pin will arrive in the next day or 2, lets see how that changes things first (i.e. one change at a time).

folder fanatic

I am really hopeful that the Saddle Adaptor Pin will work for you. Please let us know what happens.

cyclistjohn

https://www.greenspeed.com.au/newsletter5.htm#4. Short Cranks

"4. Ultra Short Cranks" is the relevant section to get you started :-)

EvilV

That was an interesting read John.

It sort of goes against my own simplistic understanding of what goes on in pedaling. I'm getting twinges in my left knee at the moment when riding my 54" geared Strida copy. It comes on when I'm going up hill as the force increases to maintain speed. I HAD thought that shorter cranks would require that more force be applied to maintain a specific power at the rear wheel, since the leverage would be shorter and hence more pressure would be needed. However, I had not thought about the amount of angle the knee joint needs to operate through, and to be honest, I can't just visualise that at this moment. I'm going to have to sit down with a pencil and do some drawings to work out how it affects the knee.

cyclistjohn

Fortunately, I don't have many knee twinges currently, but I am mindful of the consequences, so I'm keen to have as little unnecessary stress on them as possible.

Their "side effects" are interesting too. I find it easier in busy situations not to have to coordinate my static leg positions when I'm going around bends, particularly at night, & where there are high kerbs or rough road edges. Potentially they should also be a bit lighter, but I haven't found them easy to buy at a sane price. I checked the Netherlands web page where I bought mine, but he doesn't seem to stock them now. I'd like another set, maybe 145, or 150, so I suspect I'll need to buy from the USA, eg.,

https://www.gaerlan.com/bikeparts/parts/crank/crank.html

but that may mean more hunting for chainrings, as I really need 130 BCD, not 110, since the rings are like dinner plates :-) I fitted a 53 tooth ring yesterday, which was nice for more top speed, but back to more strain going up hills!

Here's another possible source:

https://bikesmithdesign.com/


When I bought the 155 cranks, I thought I'd try them on my Strida 3.2, & also remove its freewheel so I could try out a fixie :-)

However, I didn't, as it dawned on me I'd have to raise the saddle yet another 15 mm or so, & to get maximum power I already have my saddle at probably a bit too high, which means I have to take care which way to lean when I'm on a well cambered road, to put my foot (well, tiptoe actually :-)) down! To get the best out of a Strida, I feel saddle height is really vital. Just a bit too low means much more fatigue going up steep hills.

Cranks are indeed a very interesting subject, so it'd be nice to see your sketches & ideas when you've thought them out please :-)

I'm really pleased you're enjoying your Strida, a great fun bicycle to have.

EvilV

Thanks John - but you do know I'm riding a copy, don't you?

By the way - After reading your remarks this morning, I lowered my seat an inch and guess what - five miles ridden and never a knee twinge..... I hope I am onto something here. The clue to the solution was that when I rode with my left toe pushing that pedal the problem went away, so I think I was over extending the knee joint and irritating a rough patch in that knee. I used to run 25 - 30 miles a week between the ages of about 25 and 44 and although I'm pretty free of aches and pains, I do have a little tendency to notice that knee when say running up a hill, or even walking if it is steep. This isn't a problem, but it was rearing its head more and more on the Strida copy on hills. I think it is solved now though - I hope so, because I am formulating a plan to do some touring riding and pushing the triangle with some luggage on the back.

https://www.bikeforums.net/showpost.p...56&postcount=5