Author Topic: New chap with a 656 (Read 6805 times)

crogthomas · « **on:** April 04, 2007, 06:36:01 am »

Greetings, just bought myself a Proflex 656 after many years of wanting to try one of those wierd looking bikes with the linkage forks. I probably should have looked on here first for a bit more information, but it was cheap (or at least I feel like I got a good deal) and I couldn’t resist. Previous bikes have all been rigid and steel, so this is a bit of a departure for me.

I don’t even know what year it is, but heres a picture:

It has a stem marked ‘Vector 2’ that is part of the suspension linkage and the springs are both very hard elastomers. The forks have been recently powder-coated and there seems to be a few spacers or seals missing from parts of the forks since I can see gaps where it doesnt look like there should be gaps. Not too much of worry for now since I have found the exploded diagram of the forks on the K2 website and have access to a lathe to make up any bushes etc. I figure I’ll strip it down and rebuild it with new elastomers before using it.
Current components are a mix of good (LX rear mech) and not so good (bottom of the range Shimano riveted crankset and V brakes), with odd bits thrown in like the 8 speed Centera Gripshifter (on a 7 speed bike?). Things to change later I think.

I’ll have to sit down sometime and have a good read through all the threads on here, but for now I am wondering if there are any good summaries of the proflex/K2 bike range, model history and key differences between models, that sort of thing? It would help immensely to get my head round everything.

orange · « **Reply #1 on:** April 04, 2007, 06:54:53 am »

problem is where to start? There is so much info around here and if you have a peek at www.retrobike.co.uk there's catalogue scans etc there too... good luck! are you UK or USA or elsewhere?

crogthomas · « **Reply #2 on:** April 04, 2007, 09:08:40 am »

Hi, Im in the UK, just outside Reading, in the middle of Bracknell Forest. Which is nice.
I'll be having a look over at RetroBike in a mo. Thanks for the advice.

Craig

mizunole · « **Reply #3 on:** April 04, 2007, 11:29:30 am »

Here you go...

http://www.retrobike.co.uk/forum/viewtopic.php?t=1448

orange · « **Reply #4 on:** April 04, 2007, 07:08:24 pm »

and this: http://www.retrobike.co.uk/forum/viewtopic.php?t=8761

kiwi · « **Reply #5 on:** April 04, 2007, 08:35:13 pm »

proflex model numbering system very logical...all the bike numbered like that ie 656,756,856,956 all 96 model year bikes..the 6 was the lower end of real mtb bikes and the 9 was the topThe 7 8 and 9 share the same frame design,but the 9 was really tricked out.The 6 is not as easy to upgraade as the 7 and 8,but there are now options for the elastomers and i beleive risse do a shock that will work on your bike.
Sounds like your fork is missing the seals,may still be able to get a kit from iron horse with seals and bearings
At one time the 656 was the budget buy for F/S bikes and won an MBA shootout

orange · « **Reply #6 on:** April 04, 2007, 08:38:15 pm »

Does Colin have this seal kit?

kiwi · « **Reply #7 on:** April 04, 2007, 08:52:07 pm »

RK005 is the seal kit,this may hve been superseded by a seal kit for the crosslinks,but the seals themselves are the same.the orignal seals in forks of this vintage would be black and caused a lot of sticton,the white"extreme seals" as thety were called made the fork action a lot better.The crosslinks had the white/clear is seals std.
in the same document i got the seal kit number from it also has the MCU spring chart!

MCU Spring rate charts for ODS-equipped frames:
Rider weight Spring rates Spring Part # (top / bottom)
90 - 120 lbs 80 / 60 13943-12-80 / 13943-2-60
100 - 140 90 / 70 13943-12-90 / 13943-2-70
120 - 160 100 / 80 13943-12-100 / 13943-2-80
140 - 180 120 / 100 13943-12-120 / 13943-2-100
160 - 200 140 / 120 13943-12-140 / 13943-2-120
200 + 160 / 140 13943-12-160 / 13943-2-140
MCU Spring rate charts for ODS-equipped forks:
Rider weight Spring rates Spring Part # (top / bottom)
90 - 120 lbs 50 / 30 13943-11-50 / 13943-2-30
100 - 140 60 / 40 13943-11-60 / 13943-2-40
120 - 160 70 / 50 13943-11-70 / 13943-2-50
140 - 180 80 / 60 13943-11-80 / 13943-2-60
160 - 200 90 / 70 13943-11-90 / 13943-2-70
200 + 100 / 80 13943-11-100 / 13943-2-80
* For coil springs, follow Cross-Link spring rate charts.

papadahl · « **Reply #8 on:** April 05, 2007, 09:10:06 am »

Crogthomas may want the whole chart that has front and rear spring rates. It is here.

http://www.k2bike.com/01site/tech_forum/pdfs/99spring_chart.pdf

kiwi · « **Reply #9 on:** April 06, 2007, 06:06:52 pm »

Quote

Crogthomas may want the whole chart that has front and rear spring rates. It is here.

http://www.k2bike.com/01site/tech_forum/pdfs/99spring_chart.pdf

great find I had that chart but thought I had lost it for ever...i saved that one!

crogthomas · « **Reply #10 on:** April 09, 2007, 10:31:58 pm »

Quote

Crogthomas may want the whole chart that has front and rear spring rates. It is here.

http://www.k2bike.com/01site/tech_forum/pdfs/99spring_chart.pdf

Excellent, also saved for safe keeping. Just what I was looking for. Thanks everyone for all the info so far. What are the numbers in the brackets after the spring rate? (14, 16 etc)

Been reading back through posts on this forum as well. There seems to been some difference of opinion about wether the MCU spring rates given by Proflex are the shore hardness of the polyurethane or not? Has this been resolved?

Are there any recomendations for which rates to go for, for a given rider weight? They are given in overlaping ranges and the document suggests measureing the sag then making changes. Is there a precident for running at the soft or the hard end of the given ranges, or is it a personal preference thing?

Although the frame and forks seem to be esentially the same design between 6, 7, 8 and 9 models why do they all require different spring rates? Is it due to the different damping devices used (friction or oil)? And why is it not possible to swap the dampers and springs about between models? Are the frames/forks in-fact much more different than they look? Why for example does the 756 (which uses a friction damped MCU spring, right?) use different rates to the 656, which also uses a friction damped MCU spring?

Thanks again for all the help so far.
Craig

papadahl · « **Reply #11 on:** April 10, 2007, 04:44:35 am »

The numbers in brackets (14,16 etc) are the frame size.

Not sure why the difference in spring rates for friction damped MCU units.

As far as I can tell the proflex numbers do correspond to shore rates. I have access to a durometer and have measured a few. The only MCU currently available from K2 (thru a dealer) is 13943-2. (No further opton numbers like before) They say it is a medium suitable for use on the front. (rear w/rider weight up to 110 lbs). I tested it at close to 40 shore. I put two of them on my 855 front Vector 2. It is a little light for my 165lbs. After ajusting Vector 2 to the anti-pogo setting it is livable. Way better than the rocks the old MCUs had become.

Just for info, the 855r elstomers that Callum sells over at Rapid descent test at about 75 shore new. I gather they get softer as they get broken in. Have not tested them since installed.

crogthomas · « **Reply #12 on:** April 10, 2007, 08:20:26 pm »

Quote

The numbers in brackets (14,16 etc) are the frame size.

I thought it might be something like that, but does that mean that certain frame sizes should have a particular spring rate irespective of rider weight? Which seems odd. Or is it simply a guide? i.e. a large frame is likely to be ridden by a large rider of approximately 140-180lbs therefore thats the most likely spring rate that will be required.

kiwi · « **Reply #13 on:** April 10, 2007, 10:58:11 pm »

you are right,its sjut that a 20 is much more likely to have a rider near 200 lbs than a 14.The 656 is different to a 756.The 75 had friction dampers like the 855(or similar,Callum may be able to pinpoint the difference,and the 856 had the ODS units,not sure what the 956 had

papadahl · « **Reply #14 on:** April 11, 2007, 02:27:22 am »

I think what the chart indicates is mostly just what the bike came with stock from the factory as their best guess as to what would be required by a rider of that size ..like kiwi said

Rand

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Author Topic: New chap with a 656 (Read 6805 times)