Kirk Frameworks - Page 142

SPOKE · #**2116** 09-09-2022, 10:13 PM

Hot DAMN!

David Kirk · #**2117** 09-14-2022, 11:09 AM

Onesto stainless fork to pair with its Onesto Fillet frameset - made to match.

dave

OtayBW · #**2118** 09-14-2022, 03:32 PM

I can see these forks a hundred times and still have an 'Oh My...' reaction....

prototoast · #**2119** 09-26-2022, 09:30 PM

I had a question about frame stiffness, that's sort of personal, but also general enough that I think others might benefit from it.

Earlier this year, I picked up second-hand this frame you had made back in 2005.

I was really excited to try a bike with the terraplane stays, and this bike didn't disappoint. I've ridden a variety of bikes of carbon, steel, titanium, and aluminum, and this is by far the smoothest bike I've ever ridden on. Bumps just disappear underneath me, and the ride quality just feels magical.

But I've also found that when I'm cornering or descending, the bike feels a little bit too flexible for me. I don't mean this as a criticism--it would be unreasonable for me to expect a bike built for someone else to suit me perfectly, and I'm a bit heavier than the average cyclist (5'11, 190 lbs). But it's got me thinking about having one built for me, but perhaps your X-oversized tubes paired with terraplane stays.

But what I was wondering, is what I'm feeling--the combination of magically smooth on the flats, but too flexible cornering/descending two sides of the same coin? Can you have one without the other? If I had a frame made with oversized tubes and terraplane stays, ideally I'd like it to smooth out bumps but also feel rock solid around a bend at 35 mph, but what if I got the opposite?

How do you go about balancing stiffness, particularly with a frame characteristic as unique as the terraplane stays?

David Kirk · #**2120** 09-27-2022, 11:44 AM

Good question - this is 200 level stuff for sure.

Before getting to a response I feel I need to lay the groundwork on what different tube diameters are called so that we are talking about the same thing. For lugged steel bikes there are three basic sizes -

Standard - 1” top tube, 1 1/8” seat and down tube. If you have an old school steel bike like a Columbis SL Pinarello or Serotta Nova they were typically made with this size tube.

Oversize - 1 1/8” top and seat tube, 1 1/4” down tube. This is by far the most common tube size for a modern lugged steel bike.

XL or Double oversize - 1 1/4” top and seat and 1 3/8” down tube.

While one might wonder how much difference there is when adding 1/8” to the tube diameter the different is huge and easy to feel. There are some that think that tube diameter is akin to seasonal hem length and current fashion. This is not true - tube diameter has a significant and obvious impact on the way a bike feels and rides.

With that out of the way….the frameset you are riding is probably made with Oversize tubes, a 1” steerer and Gen 1 Kirk chainstays. I can’t of course be sure of the tube sizes but you can measure them easy enough. What you are probably feeling is torsional flex of the frame allowing the head tube and seat tube to flex every-so-slightly out off the same plane and this can make the handling feel less than crisp. In short the frame is twisting some and given your size this doesn’t come as a surprise.

There are two incremental ways to address this issue - first is we could make you a bike with Oversize tubes and increase the wall thickness of the main tubes. This will make the frame very slightly stiffer in torsion and should give is a more solid feel when cornering. The next option, and the better one in my mind, is to bump the tube diameter up to XL size. This will significantly increase the torsional stiffness of the frame and make it much more precise feeling on turn-in and at speed. I think that at 190 lbs this would be the way to go. Add to this the fact that with this bump up in tube size you’ll be moving to a 1 1/8” steerer and this will stiffen the fork laterally and give it a sharp ski on a fresh groomer feel.

One would typically think that going up in tube diameter could make the frame harsh riding but that isn’t necessarily the case. I use Reynolds 953 XL main tubes on my XL bikes and the tube is very thin….think .5/.3/.5 walls….and this thin tube does a great job of smoothing out the ride. If the XL tubes were the same wall as the Reynolds 725 tubes your second hand bike has (probably .9/.7/.9) the bike would probably have a harsh feeling but the super thin walls really damp out the vibrations and take the edge off of bumps. Combine this with the curved Terraplane stays and you have a torsionally stiff yet smooth riding bike.

I’m 6’4” and weight 180 lbs and have been using XL tubes on my personal bikes for a good ten years or more and it’s wonderful. The bike makes a real stable platform to make power on and the torsional stiffness allows the bike to hold and carve its line at speed or on a rough or loose surface. Would XL tubes be the choice if you weigh 150 lbs and want a buttery ride? Nope. But at 190 lbs it’s probably the right choice as long as the tube walls are suitably thin.

I hope that answers your question. Let me know if it doesn’t.

dave

Quote:

Originally Posted by prototoast

I had a question about frame stiffness, that's sort of personal, but also general enough that I think others might benefit from it.

Earlier this year, I picked up second-hand this frame you had made back in 2005.

I was really excited to try a bike with the terraplane stays, and this bike didn't disappoint. I've ridden a variety of bikes of carbon, steel, titanium, and aluminum, and this is by far the smoothest bike I've ever ridden on. Bumps just disappear underneath me, and the ride quality just feels magical.

But I've also found that when I'm cornering or descending, the bike feels a little bit too flexible for me. I don't mean this as a criticism--it would be unreasonable for me to expect a bike built for someone else to suit me perfectly, and I'm a bit heavier than the average cyclist (5'11, 190 lbs). But it's got me thinking about having one built for me, but perhaps your X-oversized tubes paired with terraplane stays.

But what I was wondering, is what I'm feeling--the combination of magically smooth on the flats, but too flexible cornering/descending two sides of the same coin? Can you have one without the other? If I had a frame made with oversized tubes and terraplane stays, ideally I'd like it to smooth out bumps but also feel rock solid around a bend at 35 mph, but what if I got the opposite?

How do you go about balancing stiffness, particularly with a frame characteristic as unique as the terraplane stays?

donevwil · #**2121** 09-27-2022, 02:41 PM

Quote:

Originally Posted by prototoast

...Earlier this year, I picked up second-hand this frame you had made back in 2005.

I was really excited to try a bike with the terraplane stays, and this bike didn't disappoint. I've ridden a variety of bikes of carbon, steel, titanium, and aluminum, and this is by far the smoothest bike I've ever ridden on. Bumps just disappear underneath me, and the ride quality just feels magical.

But I've also found that when I'm cornering or descending, the bike feels a little bit too flexible for me. I don't mean this as a criticism--it would be unreasonable for me to expect a bike built for someone else to suit me perfectly, and I'm a bit heavier than the average cyclist (5'11, 190 lbs). But it's got me thinking about having one built for me, but perhaps your X-oversized tubes paired with terraplane stays.

But what I was wondering, is what I'm feeling--the combination of magically smooth on the flats, but too flexible cornering/descending two sides of the same coin? Can you have one without the other? If I had a frame made with oversized tubes and terraplane stays, ideally I'd like it to smooth out bumps but also feel rock solid around a bend at 35 mph, but what if I got the opposite?....

It appears you and my wife need to swap made-for-someone-else terraplane Kirks. She's 5' 11", 150± while the frameset was built for someone 200+. Fits like a glove though.

prototoast · #**2122** 09-27-2022, 08:45 PM

Quote:

Originally Posted by David Kirk

With that out of the way….the frameset you are riding is probably made with Oversize tubes, a 1” steerer and Gen 1 Kirk chainstays. I can’t of course be sure of the tube sizes but you can measure them easy enough. What you are probably feeling is torsional flex of the frame allowing the head tube and seat tube to flex every-so-slightly out off the same plane and this can make the handling feel less than crisp. In short the frame is twisting some and given your size this doesn’t come as a surprise.

There are two incremental ways to address this issue - first is we could make you a bike with Oversize tubes and increase the wall thickness of the main tubes. This will make the frame very slightly stiffer in torsion and should give is a more solid feel when cornering. The next option, and the better one in my mind, is to bump the tube diameter up to XL size. This will significantly increase the torsional stiffness of the frame and make it much more precise feeling on turn-in and at speed. I think that at 190 lbs this would be the way to go. Add to this the fact that with this bump up in tube size you’ll be moving to a 1 1/8” steerer and this will stiffen the fork laterally and give it a sharp ski on a fresh groomer feel.

One would typically think that going up in tube diameter could make the frame harsh riding but that isn’t necessarily the case. I use Reynolds 953 XL main tubes on my XL bikes and the tube is very thin….think .5/.3/.5 walls….and this thin tube does a great job of smoothing out the ride. If the XL tubes were the same wall as the Reynolds 725 tubes your second hand bike has (probably .9/.7/.9) the bike would probably have a harsh feeling but the super thin walls really damp out the vibrations and take the edge off of bumps. Combine this with the curved Terraplane stays and you have a torsionally stiff yet smooth riding bike.

I’m 6’4” and weight 180 lbs and have been using XL tubes on my personal bikes for a good ten years or more and it’s wonderful. The bike makes a real stable platform to make power on and the torsional stiffness allows the bike to hold and carve its line at speed or on a rough or loose surface. Would XL tubes be the choice if you weigh 150 lbs and want a buttery ride? Nope. But at 190 lbs it’s probably the right choice as long as the tube walls are suitably thin.

I hope that answers your question. Let me know if it doesn’t.

dave

Thank you for your response. Yes, to confirm, the bike is 1 1/8" top tube, 1 1/4" down tube, 1" steerer.

I'm curious, do you use different fork blades with the XL frames, or just the larger steerer tube?

It sounds--despite my best hopes--like the frame I have just isn't quite the right frame for me, and I should start saving my money for something actually built to my ride characteristics. In terms of the XL tubing, is there a difference between the Onesto and the regular. It sounds like the top and down tube you recommend would be stainless anyway, but are there any other tubes that are better in one but not the other for a ride of my size?

David Kirk · #**2123** 09-28-2022, 11:56 AM

Cool -

Yes….I have 3 different fork blades that I choose from based on the size and weight of the rider as well as how the bike will be used. In addition one can trim the fork blade to length by taking material off the top or the bottom and this results in a real world difference in stiffness.

The main tubes of an Onesto XL and a JKS X are typically the same. On rare occasions I will use an 853 Pro tube in the front of a JKS X to get a longer butt or a thicker wall if the rider is particularly big or heavy. But that is rare.

I also have different weight chain and seat stays that get pulled out for big and/or heavy guys. I don’t use them all that often but it’s good to have them in the quiver.

Thanks for asking.

dave

Quote:

Originally Posted by prototoast

Thank you for your response. Yes, to confirm, the bike is 1 1/8" top tube, 1 1/4" down tube, 1" steerer.

I'm curious, do you use different fork blades with the XL frames, or just the larger steerer tube?

It sounds--despite my best hopes--like the frame I have just isn't quite the right frame for me, and I should start saving my money for something actually built to my ride characteristics. In terms of the XL tubing, is there a difference between the Onesto and the regular. It sounds like the top and down tube you recommend would be stainless anyway, but are there any other tubes that are better in one but not the other for a ride of my size?

donevwil · #**2124** 09-28-2022, 01:46 PM

Quote:

Originally Posted by David Kirk

Cool -

Yes….I have 3 different fork blades that I choose from based on the size and weight of the rider as well as how the bike will be used. In addition one can trim the fork blade to length by taking material off the top or the bottom and this results in a real world difference in stiffness.

The main tubes of an Onesto XL and a JKS X are typically the same. On rare occasions I will use an 853 Pro tube in the front of a JKS X to get a longer butt or a thicker wall if the rider is particularly big or heavy. But that is rare.

I also have different weight chain and seat stays that get pulled out for big and/or heavy guys. I don’t use them all that often but it’s good to have them in the quiver.

Thanks for asking.

dave

Dave,

Do you have this same flexibility with fork blades, chain and seat stays when configuring an MRB, or more specifically, one of your new max clearance MRBs?

prototoast · #**2125** 09-28-2022, 07:01 PM

Quote:

Originally Posted by David Kirk

Cool -

Yes….I have 3 different fork blades that I choose from based on the size and weight of the rider as well as how the bike will be used. In addition one can trim the fork blade to length by taking material off the top or the bottom and this results in a real world difference in stiffness.

The main tubes of an Onesto XL and a JKS X are typically the same. On rare occasions I will use an 853 Pro tube in the front of a JKS X to get a longer butt or a thicker wall if the rider is particularly big or heavy. But that is rare.

I also have different weight chain and seat stays that get pulled out for big and/or heavy guys. I don’t use them all that often but it’s good to have them in the quiver.

Thanks for asking.

dave

Thank you again for your reply. It sounds like I need to sell the not-made-for-me Kirk, and start saving up my money for a made-for-me Kirk. I really appreciate your insights.

David Kirk · #**2126** 09-28-2022, 09:27 PM

Quote:

Originally Posted by prototoast

Thank you again for your reply. It sounds like I need to sell the not-made-for-me Kirk, and start saving up my money for a made-for-me Kirk. I really appreciate your insights.

You are welcome - hit me up with any other questions that come to mind.

dave