ProFlex problems

[Brandon Libby]

I've got a potential problem that I'm hoping you guys can help me out with.

I have a ProFlex 555, an ancient bike by today's terms, I realize, but it rides as if I'm towing a parachute behind it. The pedal effort is at least three times what I'd expect it to be -as measured by a seat of the pants. I had it checked out by a reputable bicycle shop and they couldn't find anything wrong with it. The crank turns with little effort when spun by hand, the brakes are not dragging, the tire pressure is spot on, it shifts gears brilliantly, yet it absolutely wears me out in 20 minutes.

Of course, it would be easy just to blame my own fitness or the way I ride (which I have), but I've ridden Walmart bikes that require very little effort compared to mine. I would like to get this thing to where I can ride it before we move across the country otherwise, it's going to be sold and I'm not sure when, if ever, I will purchase another bicycle -which makes me sad.

Any ideas?

 

[toddz69]

I'm assuming the hubs don't have an excessive amount of drag?

Is the seat at the proper height? It looks pretty low in the pic so I'm assuming this is a fairly large frame for you?

Did you used to ride this thing and not get worn out in 20 minutes?

The rear tire looks almost flat in the pic and I'm assuming you pumped that up...

Todd Z.

 

[Christophe Noel]

Hmmm....I feel that sensation every spring.

Provided everything is properly adjusted, there's no mechanical reason why it would be slow. Even poorly maintained bearings add just a few meager watts of drag. I agree with Todd. Check your seat height. Not using 100% of your leg potential would make a huge difference.

 

[Brandon Libby]

I'm assuming the hubs don't have an excessive amount of drag?

Is the seat at the proper height? It looks pretty low in the pic so I'm assuming this is a fairly large frame for you?

Did you used to ride this thing and not get worn out in 20 minutes?

The rear tire looks almost flat in the pic and I'm assuming you pumped that up...

Todd Z.

The hubs feel great. I pulled it out of for a quick pic, the seat was lowered to hang the bike in my garage. It's always worn me out, I'm not certain why. Perhaps I shouldn't have invested in a suspension bike? I realize some peddling energy will be absorbed by the suspension, but it shouldn't be that significant ...should it?

 

[Brandon Libby]

Hmmm....I feel that sensation every spring.

Provided everything is properly adjusted, there's no mechanical reason why it would be slow. Even poorly maintained bearings add just a few meager watts of drag. I agree with Todd. Check your seat height. Not using 100% of your leg potential would make a huge difference.

I adjusted the seat height every which way, but to no avail. Could the suspension be too soft from wear, thus absorbing more pedal energy than normal? Is there even a slight chance that someone swapped the rear wheel to one with incorrect gearing? Am I just being a whiney little girl?

 

[Co-opski]

Brandon,
Nice bike and worth keeping over a walmart bike. I would check pedal bearings, wheel bearings and chain. I'm sure you could re-fresh that bike to last another 15 years.

 

[DaveInDenver]

A couple of questions. When you say the cranks spins by hand, do you mean forward? IOW, if you're cranking by hand with it up on a stand (or turned upside down), is the back wheel turning?

You mention the brakes don't drag, I assume you mean once again with it up on a stand? I've seen more than a few cases with badly routed or too long or short cables cause issues. You more often see it with ghost shifting as the suspension cycles or it changes when you get on the bike and preload the suspension. It all seems fine on the stand but goes to heck on the trail. So it wouldn't surprise me that you could be causing the brake cable to pull when on it but the problem goes away when you check it out later.

Similar weirdness can happy in other places, bearings that move with their races or on the axles and then bind with weight on the bike, for example. Maybe the freehub could be binding or dragging?

Rear suspension does suck some energy but it's marginal on cross country bikes and the Pro Flex in particular didn't travel that much, so the undamped bobbing as the elastomers flexed would be more annoying than anything. In any case by now they are probably almost solid rubber pucks so I doubt there's much travel left in the rear.

Oh, one last question, does the bike seem to slow down a lot when you stop pedaling or is the drag only apparent while pedaling? It might be as simple as a very inefficient position, hard to really say.

 

[p nut]

All good suggestions here, but I see the main problem culprit as the thing under the picture frames and behind the door.



Seriously, today's bikes are so much better than those old bikes, you're really doing yourself a disservice by not trying a new bike. I restore old bikes every now and then, and while they look pretty cool (especially this Bridgestone MB-4 I bought last year), the super steep geo, 10ft long stems, etc. don't make for a pleasant ride (for me). At least demo a new bike before spending any more money on fixing up that Proflex.

 

[monkeyrider]

The back tire appears to be flat. You must be built like a dachshund. Short legs, long torso. That saddle is so low and the top tube/long stem would have you all stretched out like it's 1993. The geometry makes sore just looking at it. Are those onza barends?

 

[gohuge]

Sell it to a collector and purchase a new mtn bike. Even the entry level bikes
from Bikes Direct will have a significantly better ride. Avoid full suspension,
unless you have $2000+ minimum to spend. It would be better to spend the
money on a good hardtail, with better fork and components, then to buy an entry-level
full suspension bike.

 

[Brandon Libby]

Thanks for all of the advice, guys. I guess the best thing to do at this point is to refurbish or replace. Cost and availability of parts will be the determining factor.

Would it be possible to convert it to single speed?

 

[DaveInDenver]

You can convert the Pro Flex to a one speed but it's not ideal. The pivot is not concentric with the bottom bracket so as the suspension cycles the effective chain stay length changes. Normally this would mean the frame is not going to work but your advantage with this frame is there's not much travel so you can compensate for this by using a chain tensioner that can flex or even an old derailleur.

 

[DaveInDenver]

Yea, here ya go!

 

[p nut]

Ohh, those Girvin shocks. Brings back (horrible) memories.

 

[Clymber]

well looking at the picture your back tire looks flat, besides that if you are riding on the road MTB tire suck. Try road slicks and that will help a lot and you have to remember since you cant lock out the rear suspension on every pedal stroke you are compressing the rear suspension and putting slack in the chain