Can my friend cycle 70 miles in 4 hours?

No.

Friend here. I'm the one that's doing it on Friday.

I have track speed of 51.8 for 400m and 1:59 for 800m. Also have 15:56 5k and 1:20 half marathon. My legs are meaty.

I'll have someone at each 20 miles for hydration and I am bringing bananas and cliff bars. Watch will click off at 8.75 miles (should be 30 minutes per split).

Give me advice.

Then you have much better ways to invest 4 hours.

XCemdee wrote:

Friend here. I'm the one that's doing it on Friday.

I have track speed of 51.8 for 400m and 1:59 for 800m. Also have 15:56 5k and 1:20 half marathon. My legs are meaty.

I'll have someone at each 20 miles for hydration and I am bringing bananas and cliff bars. Watch will click off at 8.75 miles (should be 30 minutes per split).

Give me advice.

Your 5K says that your overall aerobic fitness is very good and the 1:20 HM says that you have decent muscular endurance for running. What I worry about is your cycling-specific muscular endurance. My advice would be to try to mix up your cadence and position so that you don't use the muscles in exactly the same way for the whole 4 hours. Standing up on the pedals for brief periods is overall less efficient but will use somewhat different muscles.

The cyclists I know say that turning a big gear at a slow cadence burns out your legs while turning a small gear at a fast cadence works your aerobic system. Since for you I think the cycling-specific leg muscles will be the weak point, try to turn a fast cadence most of the time, with occcasional breaks in a bigger gear and/or standing up.

Full disclosure: I'm a lousy cyclist even for a runner, so take this advice with a grain of salt.

XCemdee wrote:

Friend here. I'm the one that's doing it on Friday.

I have track speed of 51.8 for 400m and 1:59 for 800m. Also have 15:56 5k and 1:20 half marathon. My legs are meaty.

I'll have someone at each 20 miles for hydration and I am bringing bananas and cliff bars. Watch will click off at 8.75 miles (should be 30 minutes per split).

Give me advice.

Slam the stem down, try to find a comfortable, but flat back, more road bike position. Maybe get a longer stem. Even if you don't change anything on the bike, ride with your hands right next to the stem and crouch down low to narrow your profile. See this:

Probably too late and out of your budget, but put on some low rolling resistance tires like the ones at the top of this list. If you can't put on faster tires, at least pump up the tires to the max sidewall pressure.

This actually helps out a lot; thank you!

XCemdee wrote:

This actually helps out a lot; thank you!

I don't think you'll make one loop (20 miles) at that pace. The wind and rolling resistance are a lot worse on a mountain bike.

My suggestion would be to wear real cycling tights with padding and lots of chamois cream. You will be putting a lot of stress on your butt and your vas deferens area. I had a friend who did a 100 mile bike ride with no training and wound up impotent for several months.

Finding the right seat position will help, but finding the right saddle is also very important. As your ride position changes, your seat position and the best saddle for that position changes... maybe not so much for a minor change on a road bike, but you'll be making a major change if you ride in the low tuck position.

My #1 recommendation is don't do this. One 20-mile loop would be far enough for your first attempt. I doubt if you can make it even that far at that pace on an old mountain bike. The risk of a knee injury is very high. Once you get tired and start pushing, you can put a lot of stress on the knee. Just do one loop and see how you feel. Then, you can build up to a longer distance. Better yet, ditch the mountain bike and borrow a road bike. The difference is night and day. Even so, 70 miles is too far. Build up to it.

What you're attempting is roughly the equivalent of attempting to race a marathon wearing hiking boots with only indoor training on a treadmill with a long run of 8 miles. I strongly recommend that you not attempt this.

On my old Giant Boulder 17mph was a flat out sprint effort.

On a Boardman CX with Vittoria Cross XM Pros I still wouldn't try it.

Only remote chance is to put slick tyres on it.

Jimmy21 wrote:

This thread is kind of eye opening for me. I'm training for a half iron man. 56 mile bike ride. I had just assumed 20mph would be easy and I'd be a few mph above that. All my rides have been around the city so far, so I'm always stopping and starting. I really need to get out to the country and do a long ride

A lot also depends on the bicycle. You can literally buy speed in triathlon, and 20 mph is significantly easier on a high end bicycle.

XCemdee wrote:

Friend here. I'm the one that's doing it on Friday.

.......

.......... Give me advice.

Have you ridden this old mountain bike at 17.5mph before this? You might want to try it for, say, 10 miles early this week and see how you feel. Most of us cyclists on LetsRun doubt if you can hold that pace for more than a few minutes. By 15-20 minutes, it should be obvious that you can't hold that pace for four hours.

My suggestion would be to wear real cycling tights with padding and lots of chamois cream. You will be putting a lot of stress on your butt and your vas deferens area. I had a friend who did a 100 mile bike ride with no training and wound up impotent for several months.

good word of caution here. OP, is it worth potentially screwing up your man plumbing for the lulz? my guess is that the saddle soreness will be what ends the attempt for you. it is no joke.

I am a decent 71 year old runner (consistently top 5 in age group at XC Nationals). I currently have some good commuter tires on my old mountain bike and use it for cross training 3 times/week. On a flat ride at a comfortable pace I hit 16-17 miles for an hour ride. A young, fit runner with some good tires on the bike should have a solid shot at making 70miles in 4 hours.

Jimmy21 wrote:

This thread is kind of eye opening for me. I'm training for a half iron man. 56 mile bike ride. I had just assumed 20mph would be easy and I'd be a few mph above that. All my rides have been around the city so far, so I'm always stopping and starting. I really need to get out to the country and do a long ride

If you haven't got a pretty good idea of what kind of pace you can hold for a long ride then you aren't actually training for a half ironman by any reasonable definition of "training".

The same goes for the OP. There are plenty of people who can knock off a 4 hour ride at 17.5 MPH on a decent bike and most don't have the running credentials claimed above. Virtually all of them have been putting in miles on a real bike on a real road.

As others have pointed out, on a road bike you have a chance, but on a MTB it is going to be challenging. To get the best possible shot you need to make your MTB as close to a road bike as possible.

Most important: get tires with low rolling resistance and inflate to max.

Make sure the bike is in perfect conditions,

Put on road bike clip-on pedals.

Have a comfortable saddle, maybe borrow one from a road bike of a friend.

Consider using aero-bars.

Use cycling spandex pants with padding (they should be used without underwear).

Since you are cycling only 4 hours at a good effort, I don't think butt pain is necessarily going to be a killer; pushing on the pedals eliminates some weight from the saddle. I think your chances would have have been much higher if you had a week or to to familiarize with the bike setup and cycling with clip-ons at a high cadence.

For clarification, I will most likely be borrowing padded shorts, I will be riding with a saddle height so that my legs are extended at 10º, I'll be dropping the stem down and riding in an aero position grabbing close to the stem.

Tomorrow I have a 2-3 hour easy bike ride with these additions and will update how it goes.

Ah the Dunning Kruger effect in full force.

No way in H E double hockey sticks on an old mountain bike. Road bike? maybe, but after that second hour bleep would start going down hill. Good luck and report back.

XCemdee wrote:

I'll be dropping the stem down and riding in an aero position grabbing close to the stem.

No you won't.

Getting used to staying down in an aero position and your body adapting to be able to stay somewhat comfortable for long durations like that is possibly just as difficult at first as the actual pedalling.

Your back is really going to be stiff and you're going to feel like a hunchback when you get off the bike after your first multi-hour rides. Your body will adapt and it won't be a problem after some training, but you're kidding yourself if you think you can stay aero and push for this duration without training (or at least practicing [and one week will not help]).

Rocky Mountain High wrote:

The Unkle wrote:

Hell, I am old and no bicyclist but when coming back from knee surgery I went from covering 12 miles in an hour on a mountain bike to 21 miles less than 4 weeks later.

21 miles, sure but in what time frame? 2, 3 hours?

Less than 4 weeks, plus an hour. The first 12 miles took an hour, the remaining 9 miles took less than 4 weeks.

That’s a pretty big positive split, so he probably could have gone even faster with even pacing, maybe even 21 miles in 3 weeks.

Maybe the guy is only a so-so runner, but a good cyclist.

You must use clip-on bars. No bars, no dice.

Maybe borrow padded shorts? MAYBE? Fail.