I find myself constantly having to conciously slide back on my saddle to avoid riding on the narrow nose ,its not that the saddle is tilted forward,just that it seems too far back in relation to the pedals.
My frame is a 1970s Harry Hall 21in,I wondered if modern frames had a more vertical seat tube.
Or is there an other explanation , have I got some other setting wrong ?

Have you tried sliding the saddle forward?

Yes, what LowCel is saying is - when you loosen the seat clamp (under the saddle, not the seat post to seat tube clamp), and the saddle is loose, not only will it rotate about the seat post axis & tilt but it will also slide fore & aft on the sadle rails. Even half an inch fore or aft can make all the difference to comfort.

Ken

Did we lose a reply there somewhere?

Depending upon the OPs fit it's just as likely that a few degrees of nose up will prevent his sliding forward. He can try both remedies, but a professional fit might be in order.

Doh. does it slide forward ?
Kidding,
My question was about modern frame geometry.

Some other explanation.

Was it? All modern bikes have the same geometry and all bikes from the 70s have the same geometry?

The Seat tube angle and Head tube angles will affect ride characteristics. They should not affect the fit though, which is determined by 3 contact points (5 for you literalists) being the butt, hands and feet. Distance between those and anlges of each of the individual points are what give you the "Fit".

Although it is true that in general you will find alot more "older" road bikes with shallower seat and head tube angles although that is just a generalization. Any of those can be fixed by movement of the bars / saddle.

Why do you do this? Is it because it is not comfortable on your butt riding on the nose? If so, then you need the move the saddle forward.

If not, then tell us why you are sliding your butt back.

could be your seat is too low. i rode one of my old bikes to do errands with flat pedals the other day and kept sliding back on the saddle. the saddle was too low with the thicker shoes i was wearing. you might be sliding back trying to get more leg extension.

Yes , Just that, My Selle max flite,is very comfortable when I sit with my seat bones on the widest part,but my saddle is as far forward as my campagnolo aero seat post will allow( it has quite a crank to the rear).
I start off sat on the widest part but after a few minutes I am aware that I'm forward of the wide part and have to push back .
Reading the replies has got me thinking I need to stick the bike in the car and take it to the bike shop in Inverurie,get them to look over the set up,obviouse really,but it takes someone else to point it out.
Thanks Chaps.

It sounds like your body, based on the other two contact points it has (your hands and feet), is trying to put your butt in the place it belongs. That's fine, you just have to adjust your saddle so when your butt is in that position, it is comfy.

If you lack the room to adjust further, you probably need a seatpost with less setback.

Good luck.

Here's a few shots showing my position,it looks to me that the ball of my foot ,in the first shot ,isn't vertically underneath the front part of my knee.So I have ordered a seat post with no rearward crank,see if that helps.
Can you chaps spot any other area's of my position that could be improved ?

Based on the pictures, I am thinking the top tube is way too long for you, thus making the frame one size too large. I am basing this on the fact that your arms appear to have no give while your hands are resting on the hoods.

I think you have a relatively shorter torso and relatively longer legs. It is also possible, if you lack flexibility in the back, that you might tend to sit up straight. Either or both of those could make your body try to shorten the distance from hips to hands. Which means either shifting forward on the saddle, or riding with hands on the tops. Also, if your seat is a bit too high, your hips may be shifting forward in order to shorten the distance from hips to pedals.

Maybe you can experiment with those things - fore and aft position of the saddle (using a different post without so much set back), position of hands on the bars (eventually maybe a shorter stem), and lowering the seat just a bit (like 1/2 cm).

Bike might be a little big. Saddle might be a little high. Try this: with your shoes on, put your heel on the pedal. Rotate the pedals until the pedal with the heel is at bottom, aligned with the seat tube. With your knee completely locked out and no hip rocking, your heel should barely stay in contact with the pedal, or perhaps have up to a 4mm gap, no more.

Check that your saddle is level. A little pushing back from time to time is normal, but the spot you gravitate to should be perfectly comfortable. Try rotating your pelvis forward a little, putting your sit bones in firmer contact with the saddle. Bend your elbows about 15° and see what that does. You shouldn't ride with your arms straight like that - nothing to absorb road shock and too much torso showing to the wind. To check stem length with respect to saddle position, with hands on the hoods, bend your elbows to 90° while pedaling. Your elbows should be about 2" directly in front of your knees.

Thanks for all the very usefull info,plenty to work on.
I have adjusted the seat angle very slightly,it's now fractionally up at the front and set the height so that my heel is just on the pedal at bdc,of for a ride in the moonlight to try it.
Cheers
Lee

That's what I'll be doing to fix the same issue.

Or alternately you could try bringing the cockpit closer to you by converting your quill stem to a modern threadless setup. Then you have a virtually endless supply of inexpensive stems at your disposal to dial the reach in (I'd flip the stem up too and see if that helps.)

Well the moon failed to show and it rained a bit,on the + side,the nose up did help.The seat post I ordered,arrived( gravity gap 27.2 mm x 350mm from chain reaction cycles )(i can recomend the quick delivery and price Miller2). A bit of modification to it and the saddle is 20mm further forward,so if it's half decent tommorow I will try it out.
Dunbar, how would I fit a modern threadless stem ? mine is 1in dia.
Getting there.
Lee

You need something like this.

https://www.amazon.com/Origin8-Thread...l+stem+adapter

Bike Nashbar usually has these, too.

Thanks for that chaps, I had no idea such things existed,managed to find a U.K. supplier. They ( S.J.S. cycles) also do a seat post with a crank to the front of 85 mm,it's to convert a road bike to a time trialer,a bit pricey at £65 but a usefull tool.
Rode 20 odd miles this afternoon with the new seat post and the nose up ,maybe 2deg, felt much better .
So thanks for all the replies,got me motivated enough to sort out a problem that's been annoying me for the last couple of YEARS!!
Cheers
Lee
p.s. Did you know that Dunbarr is about 20 miles east of Edinburgh out towards Berwick upon Tweed.

And you would have to consider this solution if you had the problem on a vintage frame, too.

I would say, try to ride with your elbows less straight and not locked. If you can't, the reach of the bike is too long. If reaching to the hoods is what's making you come forward on the saddle, several things: You can try a shorter stem, which moves the Hbars back. Probably should not adjust that more than 2 cm.

You can try a handlebar with less reach. If what yo have has a reach of 110 mm, you can probably find something similar down to 90 mm or so. Going shorter restricts small to normal hands like mine.

Both changes may affect the handling, though I've always adjusted to such changes readily.

If either of these changes helps you keep your hips back so your weight is supported on your sit bones, then you probably do need a frame with a shorter top tube. I tend to agree with your self-assessment of your knee position. I like to be farther back on the bike with my knees maybe 1 cm behind the KOPS position. I have put on setback seatposts to be able to achieve that.

KOPS is widely accepted as a starting point for body fore-aft positioning, but it's really very personal. Your body wants what it wants, and reading about KOPS is not going to change your biomechanics. I only use it as a reference point.

While these parts trials are an investment, they're a much less dear one than buying new frames and finding they don't work for you, or make matters worse.