Road Cycling - Straight v. Sloped

Can anyone tell me why the top tube on some bikes is sloped instead of straight? Thanks.

cheaper to build...and the bike makers haven't anything else to say "new & improved" with.

Look at the way you sit on both kinds and that should answer your question.

Designers preception that slant is stronger and better then straight. Looks better is considered a cross-trainer. I for one, don't have the real answer...

I think the sloping top tubes on today's road bikes are just a marketing ploy to appease converts from mountain biking who are acustomed to having lots of standover clearance.

The thing I have against the so-called compact frame is the idea that a S, M, and L range can be expected to ideally fit everyone.

Sloping frames also have some good points (compared to the bad ones mentioned). Because they use less material, they are supposed to be lighter. Because the rear triangle is smaller, they are supposed to be stiffer. Because of the sloping feature, they're better for smaller riders to feel more comfortable, because they can get standover clearance without sacrificing the top tube length.

All in all, it depends what kind of rider you are as to what you might like. It takes some test rides to find out what's best for you.

Originally posted by Poppaspoke
The thing I have against the so-called compact frame is the idea that a S, M, and L range can be expected to ideally fit everyone.

Sure, a lot of companies do the S, M, L thing. But, the good companies who know that fit is very important do separate sizes. This way, it's just like buying a regular frame.

Originally posted by velo
Because they use less material, they are supposed to be lighter.

isn't that made up for by the longer seatpost?

Originally posted by cycletourist
I think the sloping top tubes on today's road bikes are just a marketing ploy to appease converts from mountain biking who are acustomed to having lots of standover clearance.

And the MTBs went down that road a decade ago. The early 90s saw the trend towards sloping top-tubes on MTBs. Up until the mid-90s there were still a good number of MTBs with straight top-tubes. My first decent MTB was Specialized HardRock with a straight top-tube. My next was a Nishiki Ariel with a slightly sloped top-tube. Since then, the slope angles have increased. I think the "image" grew out of the BMX world an an effort to appeal to the "extreme sports" crowd. This is not to say that sloping tob-tubes don't hold any advantages. For some bikes or types of bikes it does. For some situations it does. For some people it does.

Yes, the frames themselves are lighter. But, with a longer seatpost, it evens itself out. Thus, they're supposed to be lighter.

The real benfit tocompact frames is to the manufacturer. They can produce the same number of frames with tooling for only 4 sizes instead of 12. Less tooling mens it's quicker to recover tooling costs and therefore you can maximise the profits and changethe desing more often.

The reality to the rider is not that apparent. I have ridden a compact Giant TCR and did'nt like it very much. Then I tried a Principia and liked that a whole lot more. Compact frames seem to be more lively but that could just be due to shorter wheelbases, especially on the Giant.

Personally I don't think they're all they supposed to be. They're not lighter becasue they still require a longer seat post which weighs more than the saved frame material

I have been riding a compact frame for over a year. I went into the purchase after riding several different manufactures versions and decided that the fit and overall comfort was suited for me. I feel that I am able to stay in the saddle longer, push hills stronger (faster) and that there was a minimum of weight savings. I didn't have to compensate the size/weight advantage by throwing in a longer seat tube and therefore adding weight.
When I went compact, I was riding a CAAD3 that I thought was the best ride for my purposes. I was putting around 5,500 miles a year on the Cannondale and I had over 6,800 miles on the compact last year. That indicates that the compact/sloping is something that suits me. It seems that frames and frame materials are like saddles and several other personal preference related items. What is good for me might be the bane of other riders.
My suggestions is to try different things and then pick what works for you. It sounds as if a couple of people on this forum have heard or read things and take those thoughts as gospel. Learn for yourself. Don't fight change. Check it out.
Signed,
Pompous Old Fart

Some compact frame manufacturers (like Thorn) make S/M/L/XL each in a short, medium and long top tube length, which means that you can really get the fit right.
How easy is it to carry a sloped TT frame over your shoulder, does it slide back?

Check the latest issue of RBR (www.roadbikerider.com). The compact frame is addressed at some length (pun intended). They don't care for them as compared to the "classical" frame design. Too many negatives compared to too few positives, by their count. RBR was especially critical of the frames' stiffness in smaller size.

Compact frames are not going to be everybody's choice.
my problems with them are the way they are marketed and sold at bike shops.
You're always encouraged to buy the smallest frame possible. In my case a size Small would require a stem of 130mm and a 350mm seat post.

The problem is that most bike frames geometry is worked out to give the best handling with a rider that will require a stem length of around 100mm to 110mm. This places the riders forward weight over or slightly behind the front axle to give the best steering responce. With compact frames this can vary substantially from rider to rider, with the result that handling cna either be twitchy or slow.
Chances are that if you can find a compact that is perfect for you, there is probably a conventional geometry frame by the same manufacturer that will suit you even better.

fit becomes function

Originally posted by MichaelW

How easy is it to carry a sloped TT frame over your shoulder, does it slide back?

My old MTB had a sloping top-tube and it really didn't effect me carrying it on my shoulder anymore than a straight top-tube. Of 'course I usually had a parrot-pack mounted but even when I didn't, it really didn't make a difference. I guess if you have a really broad shoulder then it might not pinch as much since the angle at which the top-tube meets the seat tube would generally be greater.

Compact Geometry(CG) frames look great, they look like a sleek racing machine. However, I would not agree with most people being able to get a perfect fit out of the bike. They could have to bend downwards a lot, or adopt a very upright position.

Traditional frames however do give a wide range of sizes, some even in 1cm increments. This is good enough to give everyone the perfect fit. Expecting best fit out of 4 sizes would be so tough.

Traditional frames offer a lot more comfort, less flex when riding seated. Even when I'm only 53kg, I experience a bit of flex on my steel bike which offers compact geometry. For me, I don't really trust CG frames and I would rather go for traditonal geometry frames, they look good, cool, great, everything! I don't think I'll ever settle for anything else.

Originally posted by oxologic

Traditional frames however do give a wide range of sizes, some even in 1cm increments. This is good enough to give everyone the perfect fit. Expecting best fit out of 4 sizes would be so tough.

I do not see why (on a technical level) the concepts of sloping top-tube and fine-grain sizing have to be diametrically opposed. Even mass-produced frames with sloping top-tubes have been offered in a variety of sizes. Maybe the trend has changed but it used to be that you could get sloping top-tube mountain bikes all the way from 15" to upwards of 23" in 1" and 2" increments. I don't see why compact geometry roadbikes can't be offered in as wide a range. Is it just because manufacturers are using the compact geometry concept to avoid making them in so many sizes?

Too many good points made to add much. For any given "diamond frame" size there is an optimum "fit to rider".

Adjustments to stem, bars,seat post, seat etc are methods of compromising the "fit to rider" character....of any given frame.

I've been lucky enough to own hand-built custom fitted bicycles. Too bad for those cyclists that never get to have ridden and appreciated a correctly fitting, sized, diamond-frame style bicycle, - They're really neat.

Compact frames for MTBing is a totally different kettle of fish.
In an XC MTB race the rider spens about 50% of the lap out of the saddle. So stand over clearance and nimble handling and BB stability are the most important features needed on an MTB.

A road rider spends more time in the saddl and the bike he rides has to be designed to be comfortable under that condition. Also An MTB has suspension to shield the rider from trail roughness. With a road bike it is only the frame that ias absorbing this.

A road frame has to cope with more variables than an MTB. Compact Geometry cannot realistically cope with providing a suitable solution.

I think this is why most Pro rider perfer conventiona geometry over compact. They get the best compromise between good handling, stability and ride comfort from a conventional bike than from a Compact frame. Thos e peole who ride compacts will no doubt love them, but like i said earlier, it's not everyones cup of tea. Me, I'm undecided

There is a lot of crap floating around the internet about compact frames vs traditional frames. Most of it is anecdotal. A lot of people who comment haven't spent enough time on a compact frame to talk about it.

I have ridden a traditional frame road bike for 8 years and have also been riding a compact frame for this year. There is very little difference really. When I am racing and concentrating on where to attack the last thing I am thinking about is compact vs traditional.

The new bike is certainly lighter and quicker but that is because my old bike was 2.5kg heavier, nothing to do with frame design. I took the tape measure to both bikes and the handle bars and seat are the same distance from the ground, the wheelbase was only 1 inch shorter. So any talk about a lower centre of gravity is crap, considering my body is the same height from the ground. The compact uses less material than a traditional but hardly enough to make a noticeable difference. It does have a longer seatpost but being carbon it's fairly light.

In the end I can't tell much difference from the compact to the traditional (apart from the weight) until I look down and remember which bike I am riding.

Some like traditional frames, some like compacts but don't make assumption and opinions unless you have ridden both.

CHEERS.

Mark

I have a Giant OCR1 with the compact frame. It's exactly what I needed but couldn't get with the standard frame bicycle. I have short legs but a regular sized torso. I have always had to sacrifice good standover clearance to get a decent top tube length and a comfortable riding position. With the sloping top tube I get the top tube [i.e. saddle to handlebar] length without sacrificing the the standover clearance.
Now, a person with longer legs probably would not find any advantage to the sloping top tube. And I doubt that there is any significant weight saving either way.

I've raced both standard and compact frames the last several years. Just as you can say "there is no difference" the simple fact the tubes are set at such radical angles does, in fact, change the ride.

There is a difference between compact and standard frames. The difference is so large that I prefer only one style now- standard. The exception maybe the ONCE carbon Giant but I haven't spent enough time in the saddle to give a definite opinion yet.


For sizing and standover, the compact frames are a godsend for shorter folks.

Originally posted by Waxbytes
I have short legs but a regular sized torso. I have always had to sacrifice good standover clearance to get a decent top tube length and a comfortable riding position. With the sloping top tube I get the top tube [i.e. saddle to handlebar] length without sacrificing the the standover clearance.


This was a consideration for me as well. I have short legs and a short inseam. The Specialized Sequoia Expert I purchased a few days ago has "comfort geometry", and it is a plus for me.

I am an Auxiliary Police officer and we have a bike patrol on the boardwalk. Even though I grab the smallest bike and can get the seat height to fit, the top tube is still so high as to make it difficult (and if I am not careful...painful) to stand over the frame or come to a quick stop.

Rob

Thats the aspect of compacts that the bike companies should be marketing, not light weight because that is'nt true.

If the bike fits ride it.

Psykik, I've been looking at the Sequoia as well. I'd be very interested in how you like it after you get a few miles under your belt. Looks like a great ride. Enjoy.

Originally posted by slotibartfast
Psykik, I've been looking at the Sequoia as well. I'd be very interested in how you like it after you get a few miles under your belt. Looks like a great ride. Enjoy.

I am looking forward to riding. I am waiting for the weather to improve a bit...still some ice, puddles, snow and a lot of road salt around. It is still nasty and windy on the boardwalk, my most favorite place to ride where I live. Plus with a newborn at home, it is hard to want to run out and play! I don't get enough of her!

For the little that I have ridden it...it feels much lighter and more nimble than my Crossroads. Unfortunately, my limited experiences with this week's purchase can not be more specific or technical than that. At least I have the bike now rather than wishing I had it when I was ready to start riding more regularly again.

Now I am contemplating the move from using cages (on the Crossroads) to the clipless pedals that came with the bike. That, of course is a whole new and extensively commented on topic! The bike comes with Shimano SPD. I have taken an interest in the Speedplay Frogs, concerned about the possibilities of knee strain due to limited float. Again, here I guess it is also a matter of fit and body geometry.

The boardwalk awaits me!

Rob